Elective nodal dissection for cN0 intermediate-grade parotid mucoepidermoid carcinoma: A NCDB study.

PURPOSE: To determine the occult nodal disease rate and whether elective regional lymph node dissection (RLND) confers any 10-year overall survival (OS) in cN0 intermediate-grade mucoepidermoid carcinoma (MEC) of the parotid gland. MATERIALS & METHODS: The National Cancer Database was reviewed from 2004 to 2016 on adults with cT1-4aN0M0 intermediate-grade parotid MEC undergoing resection with/without RLND. Comparisons between patients with and without RLND were made. Occult nodal rate and 10-year overall survival (OS) were determined. RESULTS: Out of 898 included patients with cN0 intermediate grade parotid MEC undergoing elective RLND, the occult nodal rate was 7.6%. This was significantly different from low-grade (3.9%) and high-grade (25.7%) cN0 disease. When stratified by pT-classification, marginal differences were identified between low-grade and intermediate-grade tumors, whereas high-grade tumors demonstrated increased occult nodal disease with low T-stage (pT1-pT2, 20.4% vs. 5.1%) and high T-stage (pT3-pT4a, 32.1% vs. 17.6%). Patients undergoing elective RLND were more often treated at an academic facility (53.8% vs. 41.2%), had higher pT3-pT4 tumors (19.2% vs. 10.4%), and more frequently underwent total/radical parotidectomy (46.0% vs. 29.9%) with adjuvant radiation therapy (53.8% vs. 41.0%) Cox-proportional hazard modeling did not identify RLND, regardless if stratified by nodal yield or pT-classification, nor nodal positivity as significant predictors of 10-year OS. CONCLUSIONS: The occult nodal disease in intermediate-grade parotid MEC is low and similar to low-grade. Elective RLND may have a limited impact on OS, though its effect on locoregional control remains unknown. LEVEL OF EVIDENCE: III.

The effect of reconstruction on positive margin rates in oral cancer: Using length of stay as a proxy measure for flap reconstruction in a national database.

PURPOSE: Planned flap reconstruction, allowing aggressive resections of oral cavity squamous cell carcinoma (OCSCC), may decrease positive surgical margins. The purpose of this study was to determine if length of stay (LOS), as a proxy measure for flap reconstruction, is associated with positive margin rates in OCSCC. MATERIALS AND METHODS: Data from the National Cancer Database was retrospectively collected for patients undergoing surgery for previously untreated clinical T1-3 OCSCC. Post-operative LOS was dichotomized between ≤4 and >4 days as a proxy measure for whether patients may have received flap reconstruction. Patients with LOS >4 days represent a diverse group, but those with a LOS ≤4 days are less likely to have undergone an oral cavity flap reconstruction. RESULTS: 10,107 patients were included, of which 5290 (52%) were clinical T1 and 4852 (48%) were clinical T2-3. 771 (8%) patients had a positive surgical margin. On multivariable logistic regression analysis, LOS ≤4 days was significantly associated with a positive margin resection in patients with clinical T2-3 tumors (OR 1.68, 95%CI 1.37-2.06) compared to patients with LOS >4 days. LOS was not associated with surgical margin status in patients with clinical T1 disease (OR 0.76, 95%CI 0.55-1.06). Patients with positive margin resections demonstrated worse overall survival (cT1: OR 1.35, 95%CI 1.06-1.72; cT2-3: OR 1.52, 95%CI 1.33-1.74). CONCLUSIONS: LOS >4 days after oral cavity cancer resection was significantly associated with negative surgical margins in clinical T2-3 oral cavity cancer, suggesting the possibility that patients undergoing flap reconstruction after resection have fewer positive surgical margins.

Trypanosoma brucei EIF4E2 cap-binding protein binds a homolog of the histone-mRNA stem-loop-binding protein.

Trypanosomatids are parasitic protozoans characterized by several unique structural and metabolic processes that include exquisite mechanisms associated with gene expression and regulation. During the initiation of protein synthesis, for instance, mRNA selection for translation seems to be mediated by different eIF4F-like complexes, which may play a significant role in parasite adaptation to different hosts. In eukaryotes, the heterotrimeric eIF4F complex (formed by eIF4E, eIF4G, and eIF4A) mediates mRNA recognition and ribosome binding and participates in various translation regulatory events. Six eIF4Es and five eIF4Gs have been described in trypanosomatids with several of these forming different eIF4F-like complexes. This has raised questions about their role in differential mRNA translation. Here we have studied further TbEIF4E2, the least known eIF4E homologue from Trypanosoma brucei, and found that it is not associated with an eIF4G homolog. It is, however, associated with mature mRNAs and binds to a histone mRNA stem-loop-binding protein (SLBP), one of two Trypanosoma SLBP homologs (TbSLBP1 and TbSLBP2). TbSLBP1 is more similar to the mammalian counterpart while TbSLBP2 is exclusive to trypanosomatids and related organisms. TbSLBP2 binds to TbEIF4E2 through a conserved central region missing in other SLBP homologs. Both SLBPs, as well as TbEIF4E2, were found to localize to the cytoplasm. TbEIF4E2 and TbSLBP2 are differentially expressed during cell culture, being more abundant in early-log phase, with TbSLBP2 also showing cell-cycle dependent expression. The new data reinforce unique aspects of the trypanosomatid eIF4Es, with the TbEIF4E2-TbSLBP complex possibly having a role in differential selection of mRNAs containing stem-loop structures.

PAKs inhibitors ameliorate schizophrenia-associated dendritic spine deterioration in vitro and in vivo during late adolescence.

Drug discovery in psychiatry has been limited to chemical modifications of compounds originally discovered serendipitously. Therefore, more mechanism-oriented strategies of drug discovery for mental disorders are awaited. Schizophrenia is a devastating mental disorder with synaptic disconnectivity involved in its pathophysiology. Reduction in the dendritic spine density is a major alteration that has been reproducibly reported in the cerebral cortex of patients with schizophrenia. Disrupted-in-Schizophrenia-1 (DISC1), a factor that influences endophenotypes underlying schizophrenia and several other neuropsychiatric disorders, has a regulatory role in the postsynaptic density in association with the NMDA-type glutamate receptor, Kalirin-7, and Rac1. Prolonged knockdown of DISC1 leads to synaptic deterioration, reminiscent of the synaptic pathology of schizophrenia. Thus, we tested the effects of novel inhibitors to p21-activated kinases (PAKs), major targets of Rac1, on synaptic deterioration elicited by knockdown expression of DISC1. These compounds not only significantly ameliorated the synaptic deterioration triggered by DISC1 knockdown but also partially reversed the size of deteriorated synapses in culture. One of these PAK inhibitors prevented progressive synaptic deterioration in adolescence as shown by in vivo two-photon imaging and ameliorated a behavioral deficit in prepulse inhibition in adulthood in a DISC1 knockdown mouse model. The efficacy of PAK inhibitors may have implications in drug discovery for schizophrenia and related neuropsychiatric disorders in general.

The streamlined genome of Phytomonas spp. relative to human pathogenic kinetoplastids reveals a parasite tailored for plants.

Members of the family Trypanosomatidae infect many organisms, including animals, plants and humans. Plant-infecting trypanosomes are grouped under the single genus Phytomonas, failing to reflect the wide biological and pathological diversity of these protists. While some Phytomonas spp. multiply in the latex of plants, or in fruit or seeds without apparent pathogenicity, others colonize the phloem sap and afflict plants of substantial economic value, including the coffee tree, coconut and oil palms. Plant trypanosomes have not been studied extensively at the genome level, a major gap in understanding and controlling pathogenesis. We describe the genome sequences of two plant trypanosomatids, one pathogenic isolate from a Guianan coconut and one non-symptomatic isolate from Euphorbia collected in France. Although these parasites have extremely distinct pathogenic impacts, very few genes are unique to either, with the vast majority of genes shared by both isolates. Significantly, both Phytomonas spp. genomes consist essentially of single copy genes for the bulk of their metabolic enzymes, whereas other trypanosomatids e.g. Leishmania and Trypanosoma possess multiple paralogous genes or families. Indeed, comparison with other trypanosomatid genomes revealed a highly streamlined genome, encoding for a minimized metabolic system while conserving the major pathways, and with retention of a full complement of endomembrane organelles, but with no evidence for functional complexity. Identification of the metabolic genes of Phytomonas provides opportunities for establishing in vitro culturing of these fastidious parasites and new tools for the control of agricultural plant disease.

eIF4F-like complexes formed by cap-binding homolog TbEIF4E5 with TbEIF4G1 or TbEIF4G2 are implicated in post-transcriptional regulation in Trypanosoma brucei.

Members of the eIF4E mRNA cap-binding family are involved in translation and the modulation of transcript availability in other systems as part of a three-component complex including eIF4G and eIF4A. The kinetoplastids possess four described eIF4E and five eIF4G homologs. We have identified two new eIF4E family proteins in Trypanosoma brucei, and define distinct complexes associated with the fifth member, TbEIF4E5. The cytosolic TbEIF4E5 protein binds cap 0 in vitro. TbEIF4E5 was found in association with two of the five TbEIF4Gs. TbIF4EG1 bound TbEIF4E5, a 47.5-kDa protein with two RNA-binding domains, and either the regulatory protein 14-3-3 II or a 117.5-kDa protein with guanylyltransferase and methyltransferase domains in a potentially dynamic interaction. The TbEIF4G2/TbEIF4E5 complex was associated with a 17.9-kDa hypothetical protein and both 14-3-3 variants I and II. Knockdown of TbEIF4E5 resulted in the loss of productive cell movement, as evidenced by the inability of the cells to remain in suspension in liquid culture and the loss of social motility on semisolid plating medium, as well as a minor reduction of translation. Cells appeared lethargic, as opposed to compromised in flagellar function per se. The minimal use of transcriptional control in kinetoplastids requires these organisms to implement downstream mechanisms to regulate gene expression, and the TbEIF4E5/TbEIF4G1/117.5-kDa complex in particular may be a key player in that process. We suggest that a pathway involved in cell motility is affected, directly or indirectly, by one of the TbEIF4E5 complexes.

Rescue of fragile X syndrome phenotypes in Fmr1 KO mice by the small-molecule PAK inhibitor FRAX486.

Fragile X syndrome (FXS) is the most common inherited form of autism and intellectual disability and is caused by the silencing of a single gene, fragile X mental retardation 1 (Fmr1). The Fmr1 KO mouse displays phenotypes similar to symptoms in the human condition--including hyperactivity, repetitive behaviors, and seizures--as well as analogous abnormalities in the density of dendritic spines. Here we take a hypothesis-driven, mechanism-based approach to the search for an effective therapy for FXS. We hypothesize that a treatment that rescues the dendritic spine defect in Fmr1 KO mice may also ameliorate autism-like behavioral symptoms. Thus, we targeted a protein that regulates spines through modulation of actin cytoskeleton dynamics: p21-activated kinase (PAK). Our results demonstrate that a potent small molecule inhibitor of group I PAKs reverses dendritic spine phenotypes in Fmr1 KO mice. Moreover, this PAK inhibitor--which we call FRAX486--also rescues seizures and behavioral abnormalities such as hyperactivity and repetitive movements, thereby supporting the hypothesis that a drug treatment that reverses the spine abnormalities can also treat neurological and behavioral symptoms. Finally, a single administration of FRAX486 is sufficient to rescue all of these phenotypes in adult Fmr1 KO mice, demonstrating the potential for rapid, postdiagnostic therapy in adults with FXS.

Small molecule inhibition of group I p21-activated kinases in breast cancer induces apoptosis and potentiates the activity of microtubule stabilizing agents.

INTRODUCTION: Breast cancer, the most common cause of cancer-related deaths worldwide among women, is a molecularly and clinically heterogeneous disease. Extensive genetic and epigenetic profiling of breast tumors has recently revealed novel putative driver genes, including p21-activated kinase (PAK)1. PAK1 is a serine/threonine kinase downstream of small GTP-binding proteins, Rac1 and Cdc42, and is an integral component of growth factor signaling networks and cellular functions fundamental to tumorigenesis. METHODS: PAK1 dysregulation (copy number gain, mRNA and protein expression) was evaluated in two cohorts of breast cancer tissues (n=980 and 1,108). A novel small molecule inhibitor, FRAX1036, and RNA interference were used to examine PAK1 loss of function and combination with docetaxel in vitro. Mechanism of action for the therapeutic combination, both cellular and molecular, was assessed via time-lapse microscopy and immunoblotting. RESULTS: We demonstrate that focal genomic amplification and overexpression of PAK1 are associated with poor clinical outcome in the luminal subtype of breast cancer (P=1.29×10(-4) and P=0.015, respectively). Given the role for PAK1 in regulating cytoskeletal organization, we hypothesized that combination of PAK1 inhibition with taxane treatment could be combined to further interfere with microtubule dynamics and cell survival. Consistent with this, administration of docetaxel with either a novel small molecule inhibitor of group I PAKs, FRAX1036, or PAK1 small interfering RNA oligonucleotides dramatically altered signaling to cytoskeletal-associated proteins, such as stathmin, and induced microtubule disorganization and cellular apoptosis. Live-cell imaging revealed that the duration of mitotic arrest mediated by docetaxel was significantly reduced in the presence of FRAX1036, and this was associated with increased kinetics of apoptosis. CONCLUSIONS: Taken together, these findings further support PAK1 as a potential target in breast cancer and suggest combination with taxanes as a viable strategy to increase anti-tumor efficacy.

Trypanosoma brucei translation initiation factor homolog EIF4E6 forms a tripartite cytosolic complex with EIF4G5 and a capping enzyme homolog.

Trypanosomes lack the transcriptional control characteristic of the majority of eukaryotes that is mediated by gene-specific promoters in a one-gene-one-promoter arrangement. Rather, their genomes are transcribed in large polycistrons with no obvious functional linkage. Posttranscriptional regulation of gene expression must thus play a larger role in these organisms. The eIF4E homolog TbEIF4E6 binds mRNA cap analogs in vitro and is part of a complex in vivo that may fulfill such a role. Knockdown of TbEIF4E6 tagged with protein A-tobacco etch virus protease cleavage site-protein C to approximately 15% of the normal expression level resulted in viable cells that displayed a set of phenotypes linked to detachment of the flagellum from the length of the cell body, if not outright flagellum loss. While these cells appeared and behaved as normal under stationary liquid culture conditions, standard centrifugation resulted in a marked increase in flagellar detachment. Furthermore, the ability of TbEIF4E6-depleted cells to engage in social motility was reduced. The TbEIF4E6 protein forms a cytosolic complex containing a triad of proteins, including the eIF4G homolog TbEIF4G5 and a hypothetical protein of 70.3 kDa, referred to as TbG5-IP. The TbG5-IP analysis revealed two domains with predicted secondary structures conserved in mRNA capping enzymes: nucleoside triphosphate hydrolase and guanylyltransferase. These complex members have the potential for RNA interaction, either via the 5' cap structure for TbEIF4E6 and TbG5-IP or through RNA-binding domains in TbEIF4G5. The associated proteins provide a signpost for future studies to determine how this complex affects capped RNA molecules.

2'-O-ribose methylation of cap2 in human: function and evolution in a horizontally mobile family.

The 5' cap of human messenger RNA consists of an inverted 7-methylguanosine linked to the first transcribed nucleotide by a unique 5'-5' triphosphate bond followed by 2'-O-ribose methylation of the first and often the second transcribed nucleotides, likely serving to modify efficiency of transcript processing, translation and stability. We report the validation of a human enzyme that methylates the ribose of the second transcribed nucleotide encoded by FTSJD1, henceforth renamed HMTR2 to reflect function. Purified recombinant hMTr2 protein transfers a methyl group from S-adenosylmethionine to the 2'-O-ribose of the second nucleotide of messenger RNA and small nuclear RNA. Neither N(7) methylation of the guanosine cap nor 2'-O-ribose methylation of the first transcribed nucleotide are required for hMTr2, but the presence of cap1 methylation increases hMTr2 activity. The hMTr2 protein is distributed throughout the nucleus and cytosol, in contrast to the nuclear hMTr1. The details of how and why specific transcripts undergo modification with these ribose methylations remains to be elucidated. The 2'-O-ribose RNA cap methyltransferases are present in varying combinations in most eukaryotic and many viral genomes. With the capping enzymes in hand their biological purpose can be ascertained.

Mandibular advancement reduces pharyngeal collapsibility by enlarging the airway rather than affecting velopharyngeal compliance.

Mandibular advancement devices (MADs) are frequently prescribed for obstructive sleep apnea (OSA) patients, but approximately one third of patients experience no therapeutic benefit. Understanding the mechanisms by which MADs prevent pharyngeal collapse may help optimize MAD therapy. This study quantified the relative contributions of changes in airspace cross-sectional area (CSA) versus changes in velopharyngeal compliance in determining MAD efficacy. Sixteen patients with moderate to severe OSA (mean apnea-hypopnea index of 32 ± 15 events/h) underwent measurements of the velopharyngeal closing pressure (PCLOSE ) during drug induced sedated endoscopy (DISE) via stepwise reductions in nasal mask pressure and recording of the intraluminal pressure with a catheter. Airspace CSA was estimated from video endoscopy. Pharyngeal compliance was defined as the slope of the area-pressure relationship of the velopharyngeal airspace. MAD therapy reduced PCLOSE from a median of 0.5 cmH2 O pre-advancement to a median of -2.6 cmH2 O post-advancement (p = 0.0009), increased the minimal CSA at the velopharynx by approximately 20 mm2 (p = 0.0067), but did not have a statistically significant effect on velopharyngeal compliance (p = 0.23). PCLOSE had a strong correlation with CSA but did not correlate with velopharyngeal compliance. Our results suggest that MADs reduce velopharyngeal collapsibility by increasing airway size as opposed to affecting velopharyngeal compliance. This contradicts the speculation of previous literature that the effectiveness of MADs is partially due to a reduction in velopharyngeal compliance resulting from stretching of the soft palate. These findings suggest that quantification of velopharyngeal CSA pre- and post-MAD advancement has potential as a biomarker to predict the success of MAD therapy.

Measuring in vitro biotransformation rates of super hydrophobic chemicals in rat liver s9 fractions using thin-film sorbent-phase dosing.

Methods for rapid and cost-effective assessment of the biotransformation potential of very hydrophobic and potentially bioaccumulative chemicals in mammals are urgently needed for the ongoing global evaluation of the environmental behavior of commercial chemicals. We developed and tested a novel solvent-free, thin-film sorbent-phase in vitro dosing system to measure the in vitro biotransformation rates of very hydrophobic chemicals in male Sprague-Dawley rat liver S9 homogenates and compared the rates to those measured by conventional solvent-delivery dosing. The thin-film sorbent-phase dosing system using ethylene vinyl acetate coated vials was developed to eliminate the incomplete dissolution of very hydrophobic substances in largely aqueous liver homogenates, to determine biotransformation rates at low substrate concentrations, to measure the unbound fraction of substrate in solution, and to simplify chemical analysis by avoiding the difficult extraction of test chemicals from complex biological matrices. Biotransformation rates using sorbent-phase dosing were 2-fold greater than those measured using solvent-delivery dosing. Unbound concentrations of very hydrophobic test chemicals were found to decline with increasing S9 and protein concentrations, causing measured biotransformation rates to be independent of S9 or protein concentrations. The results emphasize the importance of specifying both protein content and unbound substrate fraction in the measurement and reporting of in vitro biotransformation rates of very hydrophobic substances, which can be achieved in a thin-film sorbent-phase dosing system.

Oral corticosteroid use and the risk of developing avascular necrosis: A large retrospective review.

INTRODUCTION: The risk of adverse events, specifically avascular necrosis (AVN), associated with corticosteroid use is not well reported. The aim of this study was to evaluate the prevalence of AVN among patients with prior oral corticosteroid administration. METHODS: An institutional database query recognized 113,734 adult patients with oral corticosteroid administration between January 2006 and May 2017. A temporal query performed on this cohort determined that 789 had a diagnosis of AVN following oral corticosteroids. A retrospective review was performed on this cohort. Data collected included demographics, comorbidities, date of initial oral corticosteroid exposure, and time to diagnosis of AVN. Records without radiographic confirmation of AVN were excluded from analysis. Patients with cumulative lifetime dosages greater than 10,000 mg prednisone were excluded from analysis. RESULTS: A total of 789 patients with oral corticosteroid use prior to diagnosis of AVN were identified. Five hundred and seventy-two patients were excluded due to insufficient documentation of oral corticosteroid dosage, no radiographic evidence supporting the diagnosis of AVN, insufficient data confirming the temporal relationship between oral corticosteroids and AVN, and/or a cumulative dosing of >10,000 mg prednisone. This left 217 patients included in the analysis. The mean duration of use prior to diagnosis of AVN was 219 (± 374) days, and mean cumulative dose was 3314 (± 2908) mg prednisone equivalents. Mean time between diagnosis of AVN and onset of pathologic fracture was 379 (± 1046) days. CONCLUSION: For patients receiving low cumulative doses of oral corticosteroids, corticosteroids pose a small risk of development of AVN. More studies are required to better characterize risk.

Rainfall, temperature, and Classic Maya conflict: A comparison of hypotheses using Bayesian time-series analysis.

Studies published over the last decade have reached contrasting conclusions regarding the impact of climate change on conflict among the Classic Maya (ca. 250-900 CE). Some researchers have argued that rainfall declines exacerbated conflict in this civilisation. However, other researchers have found that the relevant climate variable was increasing summer temperatures and not decreasing rainfall. The goal of the study reported here was to test between these two hypotheses. To do so, we collated annually-resolved conflict and climate data, and then subjected them to a recently developed Bayesian method for analysing count-based times-series. The results indicated that increasing summer temperature exacerbated conflict while annual rainfall variation had no effect. This finding not only has important implications for our understanding of conflict in the Maya region during the Classic Period. It also contributes to the ongoing discussion about the likely impact of contemporary climate change on conflict levels. Specifically, when our finding is placed alongside the results of other studies that have examined temperature and conflict over the long term, it is clear that the impact of climate change on conflict is context dependent.

Narrowed Posterior Nasal Airway Limits Efficacy of Anterior Septoplasty.

Background: Predicting symptomatic relief after septoplasty has been difficult. Minimal cross-sectional area (mCSA) measured by acoustic rhinometry and airflow resistance (R) measured by rhinomanometry have been used to select surgical candidates with mixed success. An important assumption is that mCSA and resistance are tightly coupled, but studies have reported weak or no correlation. Recently, we proposed the Bernoulli Obstruction Theory as an explanation, where tight coupling between mCSA and R is only predicted below a critical mCSA (Acrit). Methods: The nasal airway and septum of 10 healthy subjects were reconstructed from computed tomography scans. Simulated anterior septal deviations of increasing severity were created. Computational fluid dynamics simulations were performed to quantify mCSA, resistance, and flow in the healthy septum model and four simulated septal deviation models for each subject (total of 50 models). Results: A tighter coupling between mCSA and resistance was found below Acrit, estimated to be 0.20 cm2 (a very severe deviation). Above Acrit, enlarging the mCSA had a smaller effect in patients with narrower cross-sectional area in the postvalve region (CSAPV). Conclusions: Two patterns of flow increase are expected with septoplasty. Below Acrit, enlarging mCSA predictably increases flow. Above Acrit, the effect size of increasing mCSA depends on CSAPV. Unrecognized small CSAPV may explain persistent sensation of nasal obstruction after septoplasty. Our data suggest that inferior turbinate reduction ipsilateral to a septal deviation may amplify airflow benefits after septoplasty in patients with a narrow CSAPV.

Automatic 1D 1H NMR Metabolite Quantification for Bioreactor Monitoring.

High-throughput metabolomics can be used to optimize cell growth for enhanced production or for monitoring cell health in bioreactors. It has applications in cell and gene therapies, vaccines, biologics, and bioprocessing. NMR metabolomics is a method that allows for fast and reliable experimentation, requires only minimal sample preparation, and can be set up to take online measurements of cell media for bioreactor monitoring. This type of application requires a fully automated metabolite quantification method that can be linked with high-throughput measurements. In this review, we discuss the quantifier requirements in this type of application, the existing methods for NMR metabolomics quantification, and the performance of three existing quantifiers in the context of NMR metabolomics for bioreactor monitoring.

Component Processes of Decision Making in a Community Sample of Precariously Housed Persons: Associations With Learning and Memory, and Health-Risk Behaviors.

The Iowa Gambling Task (IGT) is a widely used measure of decision making, but its value in signifying behaviors associated with adverse, "real-world" consequences has not been consistently demonstrated in persons who are precariously housed or homeless. Studies evaluating the ecological validity of the IGT have primarily relied on traditional IGT scores. However, computational modeling derives underlying component processes of the IGT, which capture specific facets of decision making that may be more closely related to engagement in behaviors associated with negative consequences. This study employed the Prospect Valence Learning (PVL) model to decompose IGT performance into component processes in 294 precariously housed community residents with substance use disorders. Results revealed a predominant focus on gains and a lack of sensitivity to losses in these vulnerable community residents. Hypothesized associations were not detected between component processes and self-reported health-risk behaviors. These findings provide insight into the processes underlying decision making in a vulnerable substance-using population and highlight the challenge of linking specific decision making processes to "real-world" behaviors.

Dinoflagellate spliced leader RNA genes display a variety of sequences and genomic arrangements.

Spliced leader (SL) trans-splicing is a common mRNA processing mechanism in dinoflagellates, in which a 22-nt sequence is transferred from the 5'-end of a small noncoding RNA, the SL RNA, to the 5'-end of mRNA molecules. Although the SL RNA gene was shown initially to be organized as tandem repeats with transcripts of 50-60 nt, shorter than most of their counterparts in other organisms, other gene organizations and transcript lengths were reported subsequently. To address the evolutionary gradient of gene organization complexity, we thoroughly examined transcript and gene organization of the SL RNA in a phylogenetically and ecologically diverse group of dinoflagellates representing four Orders. All these dinoflagellates possessed SL RNA transcripts of 50-60 nt, although in one species additional transcripts of up to 92 nt were also detected. At the genomic level, various combinations of SL RNA and 5S rRNA tandem gene arrays, including SL RNA-only, 5S rRNA-only, and mixed SL RNA-5S rRNA (SL-5S) clusters, were amplified by polymerase chain reaction for six dinoflagellates, containing intergenic spacers ranging from 88 bp to over 1.2 kb. Of these species, no SL-5S cluster was detected in Prorocentrum minimum, and only Karenia brevis showed the U6 small nuclear RNA gene associated with these mixed arrays. The 5S rRNA-only array was also found in three dinoflagellates, along with two SL-5S-adjacent arrangements found in two other species that could represent junctions. Two species contained multimeric SL exon repeats with no associated intron. These results suggest that 1) both the SL RNA tandem repeat and the SL-5S cluster genomic organizations are an "ancient" and widespread feature within the phylum of dinoflagellates and 2) rampant genomic duplication and recombination are ongoing independently in each dinoflagellate lineage, giving rise to the highly complex and diversified genomic arrangements of the SL RNA gene, while conserving the length and structure of the functional SL RNA.

Hypermethylated cap 4 maximizes Trypanosoma brucei translation.

Through trans-splicing of a 39-nt spliced leader (SL) onto each protein-coding transcript, mature kinetoplastid mRNA acquire a hypermethylated 5'-cap structure, but its function has been unclear. Gene deletions for three Trypanosoma brucei cap 2'-O-ribose methyltransferases, TbMTr1, TbMTr2 and TbMTr3, reveal distinct roles for four 2'-O-methylated nucleotides. Elimination of individual gene pairs yields viable cells; however, attempts at double knock-outs resulted in the generation of a TbMTr2-/-/TbMTr3-/- cell line only. Absence of both kinetoplastid-specific enzymes in TbMTr2-/-/TbMTr3-/- lines yielded substrate SL RNA and mRNA with cap 1. TbMTr1-/- translation is comparable with wildtype, while cap 3 and cap 4 loss reduced translation rates, exacerbated by the additional loss of cap 2. TbMTr1-/- and TbMTr2-/-/TbMTr3-/- lines grow to lower densities under normal culture conditions relative to wildtype cells, with growth rate differences apparent under low serum conditions. Cell viability may not tolerate delays at both the nucleolar Sm-independent and nucleoplasmic Sm-dependent stages of SL RNA maturation combined with reduced rates of translation. A minimal level of mRNA cap ribose methylation is essential for trypanosome viability, providing the first functional role for the cap 4.

The 2'-O-ribose methyltransferase for cap 1 of spliced leader RNA and U1 small nuclear RNA in Trypanosoma brucei.

mRNA cap 1 2'-O-ribose methylation is a widespread modification that is implicated in processing, trafficking, and translational control in eukaryotic systems. The eukaryotic enzyme has yet to be identified. In kinetoplastid flagellates trans-splicing of spliced leader (SL) to polycistronic precursors conveys a hypermethylated cap 4, including a cap 0 m7G and seven additional methylations on the first 4 nucleotides, to all nuclear mRNAs. We report the first eukaryotic cap 1 2'-O-ribose methyltransferase, TbMTr1, a member of a conserved family of viral and eukaryotic enzymes. Recombinant TbMTr1 methylates the ribose of the first nucleotide of an m7G-capped substrate. Knockdowns and null mutants of TbMTr1 in Trypanosoma brucei grow normally, with loss of 2'-O-ribose methylation at cap 1 on substrate SL RNA and U1 small nuclear RNA. TbMTr1-null cells have an accumulation of cap 0 substrate without further methylation, while spliced mRNA is modified efficiently at position 4 in the absence of 2'-O-ribose methylation at position 1; downstream cap 4 methylations are independent of cap 1. Based on TbMTr1-green fluorescent protein localization, 2'-O-ribose methylation at position 1 occurs in the nucleus. Accumulation of 3'-extended SL RNA substrate indicates a delay in processing and suggests a synergistic role for cap 1 in maturation.