Tree allocation dynamics beyond heat and hot drought stress reveal changes in carbon storage, belowground translocation and growth.

Heatwaves combined with drought affect tree functioning with as yet undetermined legacy effects on carbon (C) and nitrogen (N) allocation. We continuously monitored shoot and root gas exchange, δ13 CO2 of respiration and stem growth in well-watered and drought-treated Pinus sylvestris (Scots pine) seedlings exposed to increasing daytime temperatures (max. 42°C) and evaporative demand. Following stress release, we used 13 CO2 canopy pulse-labeling, supplemented by soil-applied 15 N, to determine allocation to plant compartments, respiration and soil microbial biomass (SMB) over 2.5 wk. Previously heat-treated seedlings rapidly translocated 13 C along the long-distance transport path, to root respiration (Rroot ; 7.1 h) and SMB (3 d). Furthermore, 13 C accumulated in branch cellulose, suggesting secondary growth enhancement. However, in recovering drought-heat seedlings, the mean residence time of 13 C in needles increased, whereas C translocation to Rroot was delayed (13.8 h) and 13 C incorporated into starch rather than cellulose. Concurrently, we observed stress-induced low N uptake and aboveground allocation. C and N allocation during early recovery were affected by stress type and impact. Although C uptake increased quickly in both treatments, drought-heat in combination reduced the above-belowground coupling and starch accumulated in leaves at the expense of growth. Accordingly, C allocation during recovery depends on phloem translocation capacity.

Hot drought reduces the effects of elevated CO2 on tree water-use efficiency and carbon metabolism.

Trees are increasingly exposed to hot droughts due to CO2 -induced climate change. However, the direct role of [CO2 ] in altering tree physiological responses to drought and heat stress remains ambiguous. Pinus halepensis (Aleppo pine) trees were grown from seed under ambient (421 ppm) or elevated (867 ppm) [CO2 ]. The 1.5-yr-old trees, either well watered or drought treated for 1 month, were transferred to separate gas-exchange chambers and the temperature gradually increased from 25°C to 40°C over a 10 d period. Continuous whole-tree shoot and root gas-exchange measurements were supplemented by primary metabolite analysis. Elevated [CO2 ] reduced tree water loss, reflected in lower stomatal conductance, resulting in a higher water-use efficiency throughout amplifying heat stress. Net carbon uptake declined strongly, driven by increases in respiration peaking earlier in the well-watered (31-32°C) than drought (33-34°C) treatments unaffected by growth [CO2 ]. Further, drought altered the primary metabolome, whereas the metabolic response to [CO2 ] was subtle and mainly reflected in enhanced root protein stability. The impact of elevated [CO2 ] on tree stress responses was modest and largely vanished with progressing heat and drought. We therefore conclude that increases in atmospheric [CO2 ] cannot counterbalance the impacts of hot drought extremes in Aleppo pine.

Verification of the susceptibility loci on 7p12.2, 10q21.2, and 14q11.2 in precursor B-cell acute lymphoblastic leukemia of childhood.

Recent genome-wide association data have implicated genetic variation at 7p12.2 (IKZF1), 10q21.2 (ARIDB5), and 14q11.2 (CEBPE) in the etiology of B-cell childhood acute lymphoblastic leukemia (ALL). To verify and further examine the relationship between these variants and ALL risk, we genotyped 1384 cases of precursor B-cell childhood ALL and 1877 controls from Germany and the United Kingdom. The combined data provided statistically significant support for an association between genotype at each of these loci and ALL risk; odds ratios (OR), 1.69 (P = 7.51 x10(-22)), 1.80 (P = 5.90 x 10(-28)), and 1.27 (P = 4.90 x 10(-6)), respectively. Furthermore, the risk of ALL increases with an increasing numbers of variant alleles for the 3 loci (OR(per-allele) = 1.53, 95% confidence interval, 1.44-1.62; P(trend) = 3.49 x 10(-42)), consistent with a polygenic model of disease susceptibility. These data provide unambiguous evidence for the role of these variants in defining ALL risk underscoring approximately 64% of cases.

Integrin genes and susceptibility to human melanoma.

Integrins are transmembrane adhesion molecules that mediate cell-cell and cell-extracellular matrix attachment. Integrins regulate cell growth, proliferation, migration and apoptosis and as a consequence, can have a potential role in tumour progression and metastasis. In this study, we investigated 19 non-synonymous variants in the coding region of the human integrin genes representing 3 beta subunits and 13 alpha subunits, for their potential role in melanoma susceptibility and survival. The variants were selected on the basis of probable functional relevance and theoretical predictions. Our data showed that no genetic variant was significantly associated with survival. However, the variants in ITGA10 and ITGA6 genes showed association with decreased risk, and variants in ITGA2, ITGAE and ITGAM were associated with increased risk of melanoma. The haplotype analysis revealed association of CA haplotype of ITGAE and TAC haplotype of ITGAX with the risk modulation. A prediction analysis of functional effect, homology modelling and multiple sequence alignments of integrin sequences from different species supported our data for linkage of variants in the ITGA2 and ITGAE genes with susceptibility. The amino acid changes in each of these integrin proteins could affect intramolecularly and/or the interaction of the heterodimers. Our experimental data indicated a possible role for some of the variant alleles and/or haplotypes of the integrin genes in melanoma susceptibility, which is augmented by the theoretical analysis performed.

Epigenetic deregulation of TCF21 inhibits metastasis suppressor KISS1 in metastatic melanoma.

Metastatic melanoma is a fatal disease due to the lack of successful therapies and biomarkers for early detection and its incidence has been increasing. Genetic studies have defined recurrent chromosomal aberrations, suggesting the location of either tumor suppressor genes or oncogenes. Transcription factor 21 (TCF21) belongs to the class A of the basic helix-loop-helix family with reported functions in early lung and kidney development as well as tumor suppressor function in the malignancies of the lung and head and neck. In this study, we combined quantitative DNA methylation analysis in patient biopsies and in their derived cell lines to demonstrate that TCF21 expression is downregulated in metastatic melanoma by promoter hypermethylation and TCF21 promoter DNA methylation is correlated with decreased survival in metastatic skin melanoma patients. In addition, the chromosomal location of TCF21 on 6q23-q24 coincides with the location of a postulated metastasis suppressor in melanoma. Functionally, TCF21 binds the promoter of the melanoma metastasis-suppressing gene, KiSS1, and enhances its gene expression through interaction with E12, a TCF3 isoform and with TCF12. Loss of TCF21 expression results in loss of KISS1 expression through loss of direct interaction of TCF21 at the KISS1 promoter. Finally, overexpression of TCF21 inhibits motility of C8161 melanoma cells. These data suggest that epigenetic downregulation of TCF21 is functionally involved in melanoma progression and that it may serve as a biomarker for aggressive tumor behavior.

Somatic alterations in the melanoma genome: a high-resolution array-based comparative genomic hybridization study.

We performed DNA microarray-based comparative genomic hybridization to identify somatic alterations specific to melanoma genome in 60 human cell lines from metastasized melanoma and from 44 corresponding peripheral blood mononuclear cells. Our data showed gross but nonrandom somatic changes specific to the tumor genome. Although the CDKN2A (78%) and PTEN (70%) loci were the major targets of mono-allelic and bi-allelic deletions, amplifications affected loci with BRAF (53%) and NRAS (12%) as well as EGFR (52%), MITF (40%), NOTCH2 (35%), CCND1 (18%), MDM2 (18%), CCNE1 (10%), and CDK4 (8%). The amplified loci carried additional genes, many of which could potentially play a role in melanoma. Distinct patterns of copy number changes showed that alterations in CDKN2A tended to be more clustered in cell lines with mutations in the BRAF and NRAS genes; the PTEN locus was targeted mainly in conjunction with BRAF mutations. Amplification of CCND1, CDK4, and other loci was significantly increased in cell lines without BRAF-NRAS mutations and so was the loss of chromosome arms 13q and 16q. Our data suggest involvement of distinct genetic pathways that are driven either through oncogenic BRAF and NRAS mutations complemented by aberrations in the CDKN2A and PTEN genes or involve amplification of oncogenic genomic loci and loss of 13q and 16q. It also emerges that each tumor besides being affected by major and most common somatic genetic alterations also acquires additional genetic alterations that could be crucial in determining response to small molecular inhibitors that are being currently pursued.

Polymorphisms in the CD28/CTLA4/ICOS genes: role in malignant melanoma susceptibility and prognosis?

The appearance of vitiligo and spontaneous regression of the primary lesion in melanoma patients illustrate a relationship between tumor immunity and autoimmunity. T lymphocytes play a major role both in tumor immunity and autoimmunity. CD28, Cytotoxic T lymphocyte antigen 4 (CTLA4) and inducible costimulator (ICOS) molecules are important secondary signal molecules in the T lymphocyte activation. Single nucleotide polymorphisms (SNPs) in the CD28/CTLA4/ICOS gene region were reported to be associated with several autoimmune diseases including, type-1 diabetes, SLE, autoimmune thyroid diseases and celiac disease. In this study, we investigated the association of SNPs in the CD28, CTLA4 and ICOS genes with the risk of melanoma. We also assessed the prognostic effect of the different polymorphisms in melanoma patients. Twenty-four tagging SNPs across the three genes and four additional SNPs were genotyped in a cohort of 763 German melanoma patients and 734 healthy German controls. Influence on prognosis was determined in 587 melanoma cases belonging to stage I or II of the disease. In general, no differences in genotype or allele frequencies were detected between melanoma patients and controls. However, the variant alleles for two polymorphisms in the CD28 gene were differentially distributed in cases and controls. Similarly no association of any polymorphism with prognosis, except for the rs3181098 polymorphism in the CD28 gene, was observed. In addition, individuals with AA genotype for rs11571323 polymorphism in the ICOS gene showed reduced overall survival. However, keeping in view the correction for multiple hypothesis testing our results suggest that the polymorphisms in the CD28, CTLA4 and ICOS genes at least do not modulate risk of melanoma and nor do those influence the disease prognosis in the investigated population.

Single-nucleotide polymorphisms in DNA-repair genes and cutaneous melanoma.

Single-nucleotide polymorphisms in different DNA-repair genes are reported to modulate risk of various cancers including melanoma. We genotyped DNA from 1186 melanoma patients and 1280 healthy controls for 13 different polymorphisms in eight DNA-repair genes. Data analyses showed that none of the polymorphisms except T241M XRCC3 was associated with an increased risk for cutaneous melanoma. Carriers of the variant alleles were associated with a decreased risk (OR 0.83; 95% CI, 0.79-0.98). Three additional polymorphisms together with T241M XRCC3 that tagged the entire gene region and the neighbouring genes KLC1, ZFYVE21 and PPP1R13B were not associated with the disease risk; neither were the inferred haplotypes. Imputation showed association of comparable magnitude with 11 non-genotyped neighbouring polymorphisms. Finally, the combination of results for all polymorphisms genotyped in the present study with published data suggests that none of the investigated polymorphisms was associated with melanoma susceptibility. We conclude that 13 non-synonymous polymorphisms in eight DNA-repair genes that are frequently investigated with respect to modulation of cancer risk in populations are not associated with susceptibility to cutaneous melanoma.

A case-control study of childhood acute lymphoblastic leukaemia and polymorphisms in the TGF-beta and receptor genes.

BACKGROUND: Inherited genetic variants in critical genes can putatively modulate susceptibility to childhood acute lymphoblastic leukemia (ALL). METHODS: We used allelic discrimination method to genotype 19 polymorphisms in the transforming growth factor-beta1 (TGF-beta1), transforming growth factor-beta receptor 1 (TGF-betaR1) and transforming growth factor-beta receptor 2 (TGF-betaR2) genes in 460 cases of childhood acute ALL and 552 ethnically matched controls. The genotyped polymorphisms included functional and tagging variants to cover the three genes in entirety. We used multidimensionality reduction (MDR) method to test effect of multiple genes on disease susceptibility. In order to increase statistical power and detect susceptibility variants not directly genotyped in this study, we used imputation using HapMap data. RESULTS: None of the genotyped polymorphisms or the consequent haplotypes showed any association with risk modulation. The results, however, did show a marginal association (odds ratio OR 0.76, 95% confidence interval CI 0.59-0.97) of the variant allele for the rs10417924 polymorphism located at 3'untranslated region of the TGF-beta1 gene with the B-cell lineage ALL. No other polymorphism showed any association with childhood ALL susceptibility. A signal of marginal significance for the rs10417924 polymorphism in the TGF-beta1 gene in B-cell lineage ALL showed up with both MDR and imputation techniques. CONCLUSION: These data rule out the role of polymorphisms in the TGF-beta1, TGF-betaR1 and TGF-betaR2 genes in susceptibility to childhood ALL. However, for B-lineage ALL, the role of the rs10417924 polymorphism in TGF-beta1 gene needs further investigation.

Single nucleotide polymorphisms in DNA repair genes XRCC1 and APEX1 in progression and survival of primary cutaneous melanoma patients.

Single nucleotide polymorphisms, besides influencing susceptibility can potentially alter progression and survival in melanoma patients. In this study we evaluated the association of polymorphisms in the base-excision repair genes XRCC1 and APEX1 with overall survival (OS), metastasis-free survival (MFS) and survival following the first metastasis (SFM) in patients with cutaneous melanoma. We genotyped the D148E APEX1, -77 T>C XRCC1, R280H XRCC1, and R399Q XRCC1 polymorphisms in 400 German melanoma patients (Tx, N0, M0) using an allelic discrimination method. The results were correlated with the patient follow-up parameters. The significant association detected between the R399Q XRCC1 polymorphism and MFS was also evaluated in 529 Spanish melanoma patients. In a Kaplan-Meier survival model the AA genotype of the polymorphism showed a median OS of 24.4 years compared to 11.5 years for two other genotypes. Similarly patients with the AA genotype showed median MFS of 20.9 years compared to 5.3 years for two other genotypes. In a multivariate Cox proportional hazard model, the AA genotype was associated with a hazard ratio (HR) of 0.40, 95% (CI 0.21-0.78, p=0.007) for MFS and 0.32 (95% CI 0.11-0.90, p=0.03) for OS in 400 German melanoma patients. The decreased risk of metastasis was confirmed by adding 529 Spanish melanoma patients with a combined HR of 0.40 (95% CI 0.24-0.68, p=0.0006). A significant association with SFM was also found for -77 T>C XRCC1 (HR 1.73, 95% CI 1.02-2.94, p=0.04). Our results show that non-synonymous variants or those located in potential regulatory regions of DNA repair genes probably influence the disease outcome in melanoma patients and have potentially significant implications for patient surveillance and tailored treatment.

Multiple melanomas after treatment for Hodgkin lymphoma in a non-Dutch p16-Leiden mutation carrier with 2 MC1R high-risk variants.

BACKGROUND: A 19-base pair germline deletion in exon 2 of the CDKN2A (cyclin-dependent kinase inhibitor 2A) gene (Leiden mutation) has been detected in Dutch families with familial melanomas. The penetrance of CDKN2A mutations varies widely and is influenced by environmental and unrelated genetic factors such as variants in the MC1R gene. OBSERVATIONS: We describe a 25-year-old German woman who developed 8 invasive melanomas and 6 in situ melanomas after radiation therapy and polychemotherapy for Hodgkin lymphoma. Genetic testing revealed a constitutional CDKN2A Leiden mutation in the proband and her sister, mother, and mother's sister. The proband also carried high-risk MC1R variant alleles R151C and R160W, which she had inherited from her father and her mother, respectively. The less affected mutation carrier sister did not have high-risk MC1R variant alleles. Analysis of DNA from paraffin-embedded tissues showed loss of heterozygosity at CDKN2A loci in all 3 melanomas studied but not in Hodgkin lymphoma. The pedigree revealed several types of cancers on both sides of the family, but no Dutch ancestors were found. No mutations in the CDK4, B-raf, and N-ras genes were detected either in the germline or in tumors from the patient. CONCLUSION: This study shows the variability of the penetrance of the CDKN2A Leiden mutation within the same family, which could be due to genetic or exogenous factors.

Water availability as dominant control of heat stress responses in two contrasting tree species.

Heat waves that trigger severe droughts are predicted to increase globally; however, we lack an understanding of how trees respond to the combined change of extreme temperatures and water availability. Here, we studied the impacts of two consecutive heat waves as well as post-stress recovery in young Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) and Robinia pseudoacacia L. (black locust) growing under controlled conditions. Responses were compared under water supply close to the long-term average and under reduced irrigation to represent drought. Exposure to high temperatures (+10 °C above ambient) and vapour pressure deficit strongly affected the trees in terms of water relations, photosynthesis and growth. Douglas-fir used water resources conservatively, and transpiration decreased in response to mild soil water limitation. In black locust, heat stress led to pronounced tree water deficits (stem diameter shrinkage), accompanied by leaf shedding to alleviate stress on the hydraulic system. The importance of water availability during the heat waves became further apparent by a concurrent decline in photosynthesis and stomatal conductance with increasing leaf temperatures in both species, reaching the lowest rates in the heat-drought treatments. Stress severity determined both the speed and the amount of recovery. Upon release of stress, photosynthesis recovered rapidly in drought-treated black locust, while it remained below control rates in heat (t = -2.4, P < 0.05) and heat-drought stressed trees (t = 2.96, P < 0.05). In Douglas-fir, photosynthesis recovered quickly, while water-use efficiency increased in heat-drought trees because stomatal conductance remained reduced (t = -2.92, P < 0.05). Moreover, Douglas-fir was able to compensate for stem-growth reductions following heat (-40%) and heat-drought stress (-68%), but most likely at the expense of storage and other growth processes. Our results highlight the importance of studying heat waves alongside changes in water availability. They further suggest that we should look beyond the actual stress event to identify lagged effects and acclimation processes that may determine tree resilience in the long term.

TERT promoter mutations in familial and sporadic melanoma.

Cutaneous melanoma occurs in both familial and sporadic forms. We investigated a melanoma-prone family through linkage analysis and high-throughput sequencing and identified a disease-segregating germline mutation in the promoter of the telomerase reverse transcriptase (TERT) gene, which encodes the catalytic subunit of telomerase. The mutation creates a new binding motif for Ets transcription factors and ternary complex factors (TCFs) near the transcription start and, in reporter gene assays, caused up to twofold increase in transcription. We then screened the TERT promoter in sporadic melanoma and observed recurrent ultraviolet signature somatic mutations in 125 of 168 (74%) of human cell lines derived from metastatic melanomas, 45 of 53 corresponding metastatic tumor tissues (85%), and 25 of 77 (33%) primary melanomas. The majority of those mutations occurred at two positions in the TERT promoter and also generated binding motifs for Ets/TCF transcription factors.

Association of inherited variation in Toll-like receptor genes with malignant melanoma susceptibility and survival.

The family of Toll-like receptors (TLRs) is critical in linking innate and acquired immunity. Polymorphisms in the genes encoding TLRs have been associated with autoimmune diseases and cancer. We investigated the genetic variation of TLR genes and its potential impact on melanoma susceptibility and patient survival. The study included 763 cutaneous melanoma cases recruited in Germany and 736 matched controls that were genotyped for 47 single nucleotide polymorphisms (SNPs) in 8 TLR genes. The relationship between genotype, disease status and survival was investigated taking into account patient and tumor characteristics, and melanoma treatment. Analysis of 7 SNPs in TLR2, 7 SNPs in TLR3 and 8 SNPs in TLR4 showed statistically significant differences in distribution of inferred haplotypes between cases and controls. No individual polymorphism was associated with disease susceptibility except for the observed tendency for TLR2-rs3804099 (odds ratio OR  = 1.15, 95% CI 0.99-1.34, p = 0.07) and TLR4-rs2149356 (OR = 0.85, 95% CI 0.73-1.00, p = 0.06). Both polymorphisms were part of the haplotypes associated with risk modulation. An improved overall survival (Hazard ratio HR 0.53, 95% CI 0.32-0.88) and survival following metastasis (HR 0.55, 95% CI 0.34-0.91) were observed in carriers of the variant allele (D299G) of TLR4-rs4986790. In addition various TLR2, TLR4 and TLR5 haplotypes were associated with increased overall survival. Our results point to a novel association between TLR gene variants and haplotypes with melanoma survival. Our data suggest a role for the D299G polymorphism in the TLR4 gene in overall survival and a potential link with systemic treatment at stage IV of the disease. The polymorphic amino acid residue, located in the ectodomain of TLR4, can have functional consequences.

Variation in CDKN2A at 9p21.3 influences childhood acute lymphoblastic leukemia risk.

Using data from a genome-wide association study of 907 individuals with childhood acute lymphoblastic leukemia (cases) and 2,398 controls and with validation in samples totaling 2,386 cases and 2,419 controls, we have shown that common variation at 9p21.3 (rs3731217, intron 1 of CDKN2A) influences acute lymphoblastic leukemia risk (odds ratio = 0.71, P = 3.01 x 10(-11)), irrespective of cell lineage.

ARLTS1 polymorphisms and basal cell carcinoma of the skin.

Polymorphisms in the ARLTS1 gene, a member of the Ras super-family, have been associated with susceptibility in different cancer types. The involvement of the gene in apoptotic signalling motivated us to study the role of ARLTS1 polymorphic variations in basal cell carcinoma of the skin (BCC). In a case-control study, 529 cases diagnosed with BCC and 533 controls from Hungary, Romania and Slovakia were genotyped for the S99S (297G>A), P131L (392C>T), L132L (396G>C), C148R (442T>C) and W149X (446G>A) polymorphisms in the ARLTS1 gene. No significant association between any of the single nucleotide polymorphisms (SNP) and risk of BCC (S99S, odds ratio (OR) 0.96, 95% confidence interval (CI) 0.601.53; P131L, OR 1.31 95%CI 0.742.31; L132L, OR 0.50, 95%CI 0.027.07; C148R, OR 0.50, 95%CI 0.691.18; and W149X, OR 1.01, 95%CI 0.372.79) was detected. Furthermore, no significant difference in the distribution of haplotypes due to five polymorphisms in the ARLTS1 gene was found between the BCC cases and controls. Our data rule out an association between variants in ARLTS1 and risk of BCC in the investigated population.

Differential gene expression in melanocytic nevi with the V600E BRAF mutation.

We studied gene expression in 18 melanocytic nevi with and four nevi without the V600E mutation in the BRAF gene using HG-U133A 2.0 microarray with 22,277 transcripts. Data analysis revealed 92 genes up-regulated and 105 genes down-regulated in nevi with the mutation compared to nevi without mutation. Pathway analysis showed that differentially regulated genes mapped to 10 genetic networks. The major network included genes involved in cell death, cell cycle, and cellular growth and proliferation. Up-regulated genes in nevi with the mutation included CDKN2A, CDKN1C, and MITF; whereas down-regulated genes included those involved in apoptotic and other pathways. Principal component analysis identified 22 probe sets (20 genes) that caused separate segregation of nevi with and without mutations. In conclusion, our data showed differences in gene expression between nevi with and without the V600E BRAF mutation. Moreover, nevi with mutations showed over-expression of genes involved in melanocytic senescence and cell cycle inhibition.

B-RAF and N-RAS mutations are preserved during short time in vitro propagation and differentially impact prognosis.

In melanoma, the RAS/RAF/MEK/ERK signalling pathway is an area of great interest, because it regulates tumor cell proliferation and survival. A varying mutation rate has been reported for B-RAF and N-RAS, which has been largely attributed to the differential source of tumor DNA analyzed, e.g., fixed tumor tissues or in vitro propagated melanoma cells. Notably, this variation also interfered with interpreting the impact of these mutations on the clinical course of the disease. Consequently, we investigated the mutational profile of B-RAF and N-RAS in biopsies and corresponding cell lines from metastatic tumor lesions of 109 melanoma patients (AJCC stage III/IV), and its respective impact on survival. 97 tissue biopsies and 105 biopsy-derived cell lines were screened for B-RAF and N-RAS mutations by PCR single strand conformation polymorphism and DNA sequencing. Mutations were correlated with patient survival data obtained within a median follow-up time of 31 months. B-RAF mutations were detected in 55% tissues and 51% cell lines, N-RAS mutations in 23% tissues and 25% cell lines, respectively. There was strong concordance between the mutational status of tissues and corresponding cell lines, showing a differing status for B-RAF in only 5% and N-RAS in only 6%, respectively. Patients with tumors carrying mutated B-RAF showed an impaired median survival (8.0 versus 11.8 months, p = 0.055, tissues; 7.1 versus 9.3 months, p = 0.068, cell lines), whereas patients with N-RAS-mutated tumors presented with a favorable prognosis (median survival 12.5 versus 7.9 months, p = 0.084, tissues; 15.4 versus 6.8 months, p = 0.0008, cell lines), each in comparison with wildtype gene status. Multivariate analysis qualified N-RAS (p = 0.006) but not B-RAF mutation status as an independent prognostic factor of overall survival. Our findings demonstrate that B-RAF and N-RAS mutations are well preserved during short term in vitro propagation and, most importantly, differentially impact the outcome of melanoma patients.

ARLTS1 variants and melanoma risk.

Variants in the tumor suppressor gene ARLTS1 (ADP-ribosylation factor-like tumor-suppressor gene 1) have been shown to influence familial cancer risk. Both Cys148Arg and Trp149Stop were associated with an increased risk of familial or high-risk familial breast cancer, respectively. We studied the impact of these gene variants on melanoma risk, investigating 351 melanoma patients and 804 control subjects. While ARLTS1 Trp149Stop did not influence melanoma risk (OR = 0.83, 95% CI = 0.37-1.88, p = 0.65), Cys148Arg revealed a statistically significant association with an increased risk for heterozygous carriers (OR = 1.43, 95% CI = 1.05-1.95, p = 0.02). An additional risk enhancement, though statistically non-significant, was observed in individuals with multiple melanomas (OR = 2.33, 95% CI = 0.87-6.26, p = 0.08).

The nucleoporin RanBP2 has SUMO1 E3 ligase activity.

Posttranslational modification with SUMO1 regulates protein/protein interactions, localization, and stability. SUMOylation requires the E1 enzyme Aos1/Uba2 and the E2 enzyme Ubc9. A family of E3-like factors, PIAS proteins, was discovered recently. Here we show that the nucleoporin RanBP2/Nup358 also has SUMO1 E3-like activity. RanBP2 directly interacts with the E2 enzyme Ubc9 and strongly enhances SUMO1-transfer from Ubc9 to the SUMO1 target Sp100. The E3-like activity is contained within a 33 kDa domain of RanBP2 that lacks RING finger motifs and does not resemble PIAS family proteins. Our findings place SUMOylation at the cytoplasmic filaments of the NPC and suggest that, at least for some substrates, modification and nuclear import are linked events.