An IDR-dependent mechanism for nuclear receptor control of Mediator interaction with RNA polymerase II.

The essential Mediator (MED) coactivator complex plays a well-understood role in regulation of basal transcription in all eukaryotes, but the mechanism underlying its role in activator-dependent transcription remains unknown. We investigated modulation of metazoan MED interaction with RNA polymerase II (RNA Pol II) by antagonistic effects of the MED26 subunit and the CDK8 kinase module (CKM). Biochemical analysis of CKM-MED showed that the CKM blocks binding of the RNA Pol II carboxy-terminal domain (CTD), preventing RNA Pol II interaction. This restriction is eliminated by nuclear receptor (NR) binding to CKM-MED, which enables CTD binding in a MED26-dependent manner. Cryoelectron microscopy (cryo-EM) and crosslinking-mass spectrometry (XL-MS) revealed that the structural basis for modulation of CTD interaction with MED relates to a large intrinsically disordered region (IDR) in CKM subunit MED13 that blocks MED26 and CTD interaction with MED but is repositioned upon NR binding. Hence, NRs can control transcription initiation by priming CKM-MED for MED26-dependent RNA Pol II interaction.

Kinetic and adsorption isotherm studies of Malachite Green dye onto surfactant-tailored alginate hydrogel beads: An influence of surfactant hydrophobicity.

This study details the synthesis and characterization of surfactant-modified sodium alginate hydrogel beads crosslinked with Ba2+ ions through ionotropic gelation. Cationic surfactants such as, dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and butanediyl-α,ω-bis-(dimethyldodecylammonium bromide) (GEM), were employed in the modification process. The surfactant-modified ALG-DTAB, ALG-DDAB, and ALG-GEM beads were investigated for the removal of cationic dye Malachite Green (MG) to elucidate the impact of hydrophobicity of amphiphiles on the adsorption process. The characterizations were carried out using Rheometry, Field Emission Scanning Electron Microscopy (FESEM), Infrared Spectroscopy (IR), and Energy Dispersive X-ray Spectroscopy (EDX). Under optimized conditions, ALG-GEM and ALG-DDAB demonstrated highest maximum adsorption capacity (Qmax > 700 mgg-1). The adsorption data fitted well to pseudo-second order kinetic and Langmuir adsorption models, suggesting the involvement of chemisorption phenomena with notable contributions from pore diffusion. The effects of pH, initial dye concentration, adsorbent dose, temperature, and competing ions on the removal of MG were investigated. Interestingly, ALG-GEM beads exhibited an increase in adsorption capacity with rising pH and a subsequent decrease with increasing temperature, showcasing optimal adsorption at pH 7.0 and 25 °C. The study proposes that ALG beads modified with cationic surfactants with higher hydrophobicity could offer a promising avenue in wastewater treatment processes.

Regulation of the RNA polymerase II pre-initiation complex by its associated coactivators.

The RNA polymerase II (Pol II) pre-initiation complex (PIC) is a critical node in eukaryotic transcription regulation, and its formation is the major rate-limiting step in transcriptional activation. Diverse cellular signals borne by transcriptional activators converge on this large, multiprotein assembly and are transduced via intermediary factors termed coactivators. Cryogenic electron microscopy, multi-omics and single-molecule approaches have recently offered unprecedented insights into both the structure and cellular functions of the PIC and two key PIC-associated coactivators, Mediator and TFIID. Here, we review advances in our understanding of how Mediator and TFIID interact with activators and affect PIC formation and function. We also discuss how their functions are influenced by their chromatin environment and selected cofactors. We consider how, through its multifarious interactions and functionalities, a Mediator-containing and TFIID-containing PIC can yield an integrated signal processing system with the flexibility to determine the unique temporal and spatial expression pattern of a given gene.

Two target gene activation pathways for orphan ERR nuclear receptors.

Estrogen-related receptors (ERRα/ß/γ) are orphan nuclear receptors that function in energy-demanding physiological processes, as well as in development and stem cell maintenance, but mechanisms underlying target gene activation by ERRs are largely unknown. Here, reconstituted biochemical assays that manifest ERR-dependent transcription have revealed two complementary mechanisms. On DNA templates, ERRs activate transcription with just the normal complement of general initiation factors through an interaction of the ERR DNA-binding domain with the p52 subunit of initiation factor TFIIH. On chromatin templates, activation by ERRs is dependent on AF2 domain interactions with the cell-specific coactivator PGC-1α, which in turn recruits the ubiquitous p300 and MED1/Mediator coactivators. This role of PGC-1α may also be fulfilled by other AF2-interacting coactivators like NCOA3, which is shown to recruit Mediator selectively to ERRß and ERRγ. Importantly, combined genetic and RNA-seq analyses establish that both the TFIIH and the AF2 interaction-dependent pathways are essential for ERRß/γ-selective gene expression and pluripotency maintenance in embryonic stem cells in which NCOA3 is a critical coactivator.

Mediator subunit MED1 is required for E2A-PBX1-mediated oncogenic transcription and leukemic cell growth.

The chimeric transcription factor E2A-PBX1, containing the N-terminal activation domains of E2A fused to the C-terminal DNA-binding domain of PBX1, results in 5% of pediatric acute lymphoblastic leukemias (ALL). We recently have reported a mechanism for RUNX1-dependent recruitment of E2A-PBX1 to chromatin in pre-B leukemic cells; but the subsequent E2A-PBX1 functions through various coactivators and the general transcriptional machinery remain unclear. The Mediator complex plays a critical role in cell-specific gene activation by serving as a key coactivator for gene-specific transcription factors that facilitates their function through the RNA polymerase II transcriptional machinery, but whether Mediator contributes to aberrant expression of E2A-PBX1 target genes remains largely unexplored. Here we show that Mediator interacts directly with E2A-PBX1 through an interaction of the MED1 subunit with an E2A activation domain. Results of MED1 depletion by CRISPR/Cas9 further indicate that MED1 is specifically required for E2A-PBX1-dependent gene activation and leukemic cell growth. Integrated transcriptome and cistrome analyses identify pre-B cell receptor and cell cycle regulatory genes as direct cotargets of MED1 and E2A-PBX1. Notably, complementary biochemical analyses also demonstrate that recruitment of E2A-PBX1 to a target DNA template involves a direct interaction with DNA-bound RUNX1 that can be further stabilized by EBF1. These findings suggest that E2A-PBX1 interactions with RUNX1 and MED1/Mediator are of functional importance for both gene-specific transcriptional activation and maintenance of E2A-PBX1-driven leukemia. The MED1 dependency for E2A-PBX1-mediated gene activation and leukemogenesis may provide a potential therapeutic opportunity by targeting MED1 in E2A-PBX1+ pre-B leukemia.

Efficacy of a small molecule inhibitor of the transcriptional cofactor PC4 in prevention and treatment of non-small cell lung cancer.

The human positive coactivator 4 (PC4) was originally identified as a multi-functional cofactor capable of mediating transcription activation by diverse gene- and tissue-specific activators. Recent studies suggest that PC4 might also function as a novel cancer biomarker and therapeutic target for different types of cancers. siRNA knockdown studies indicated that down-regulation of PC4 expression could inhibit tumorigeneicity of A549 non-small cell lung cancer tumor model in nude mice. Here we show that AG-1031, a small molecule identified by high throughput screening, can inhibit the double-stranded DNA binding activity of PC4, more effectively than its single-stranded DNA binding activity. AG-1031 also specifically inhibited PC4-dependent transcriptional activation in vitro using purified transcription factors. AG-1031 inhibited proliferation of several cultured cell lines derived from non-small cell lung cancers (NSCLC) and growth of tumors that formed from A549 cell xenografts in immuno-compromised mice. Moreover, pre-injection of AG-1031 in these mice not only reduced tumor size, but also prevented tumor formation in 20% of the animals. AG-1031 treated A549 cells and tumors from AG-1031 treated animals showed a significant decrease in the levels of both PC4 and VEGFC, a key mediator of angiogenesis in cancer. On the other hand, all tested mice remained constant weight during animal trials. These results demonstrated that AG-1031 could be a potential therapy for PC4-positive NSCLC.

ZBTB1 Regulates Asparagine Synthesis and Leukemia Cell Response to L-Asparaginase.

Activating transcription factor 4 (ATF4) is a master transcriptional regulator of the integrated stress response (ISR) that enables cell survival under nutrient stress. The mechanisms by which ATF4 couples metabolic stresses to specific transcriptional outputs remain unknown. Using functional genomics, we identified transcription factors that regulate the responses to distinct amino acid deprivation conditions. While ATF4 is universally required under amino acid starvation, our screens yielded a transcription factor, Zinc Finger and BTB domain-containing protein 1 (ZBTB1), as uniquely essential under asparagine deprivation. ZBTB1 knockout cells are unable to synthesize asparagine due to reduced expression of asparagine synthetase (ASNS), the enzyme responsible for asparagine synthesis. Mechanistically, ZBTB1 binds to the ASNS promoter and promotes ASNS transcription. Finally, loss of ZBTB1 sensitizes therapy-resistant T cell leukemia cells to L-asparaginase, a chemotherapeutic that depletes serum asparagine. Our work reveals a critical regulator of the nutrient stress response that may be of therapeutic value.

A validated novel preoperative index to predict the extent of intraperitoneal contamination in patients with acute abdominal pathology: A cohort study.

AIMS: To investigate whether an intraperitoneal contamination index (ICI) derived from combined preoperative levels of C-reactive protein, lactate, neutrophils, lymphocytes and albumin could predict the extent of intraperitoneal contamination in patients with acute abdominal pathology. METHODS: Patients aged over 18 who underwent emergency laparotomy for acute abdominal pathology between January 2014 and October 2018 were randomly divided into primary and validation cohorts. The proposed intraperitoneal contamination index was calculated for each patient in each cohort. Receiver operating characteristic curve analysis was performed to determine discrimination of the index and cut-off values of preoperative intraperitoneal contamination index that could predict the extent of intraperitoneal contamination. RESULTS: Overall, 468 patients were included in this study; 234 in the primary cohort and 234 in the validation cohort. The analyses identified intraperitoneal contamination index of 24.77 and 24.32 as cut-off values for purulent contamination in the primary cohort (area under the curve (AUC): 0.73, P < 0.0001; sensitivity: 84%, specificity: 60%) and validation cohort (AUC: 0.83, P < 0.0001; sensitivity: 91%, specificity: 69%), respectively. Receiver operating characteristic curve analysis also identified intraperitoneal contamination index of 33.70 and 33.41 as cut-off values for feculent contamination in the primary cohort (AUC: 0.78, P < 0.0001; sensitivity: 87%, specificity: 64%) and validation cohort (AUC: 0.79, P < 0.0001; sensitivity: 86%, specificity: 73%), respectively. CONCLUSIONS: As a predictive measure which is derived purely from biomarkers, intraperitoneal contamination index may be accurate enough to predict the extent of intraperitoneal contamination in patients with acute abdominal pathology and to facilitate decision-making together with clinical and radiological findings.

AID-RNA polymerase II transcription-dependent deamination of IgV DNA.

Activation-induced deoxycytidine deaminase (AID) initiates somatic hypermutation (SHM) in immunoglobulin variable (IgV) genes to produce high-affinity antibodies. SHM requires IgV transcription by RNA polymerase II (Pol II). A eukaryotic transcription system including AID has not been reported previously. Here, we reconstitute AID-catalyzed deamination during Pol II transcription elongation in conjunction with DSIF transcription factor. C→T mutations occur at similar frequencies on non-transcribed strand (NTS) and transcribed strand (TS) DNA. In contrast, bacteriophage T7 Pol generates NTS mutations predominantly. AID-Pol II mutations are strongly favored in WRC and WGCW overlapping hot motifs (W = A or T, R = A or G) on both DNA strands. Single mutations occur on 70% of transcribed DNA clones. Mutations are correlated over a 15 nt distance in multiply mutated clones, suggesting that deaminations are catalyzed processively within a stalled or backtracked transcription bubble. Site-by-site comparisons for biochemical and human memory B-cell mutational spectra in an IGHV3-23*01 target show strongly favored deaminations occurring in the antigen-binding complementarity determining regions (CDR) compared to the framework regions (FW). By exhibiting consistency with B-cell SHM, our in vitro data suggest that biochemically defined reconstituted Pol II transcription systems can be used to investigate how, when and where AID is targeted.

Use of combined laboratory and ultrasonography results to select patients for biliary tract imaging or intervention: a retrospective cohort study.

AIM: To determine whether combined laboratory and ultrasonography results can be used to select patients for biliary tract imaging (BTI) or intervention. BACKGROUND: Despite ongoing research, selection of patients with suspected CBD stone (CBDS) for BTI or direct intervention without imaging is still a subject of debate. METHODS: Patients aged≥18 with symptomatic gallstone disease (SGD) who underwent MRCP over 3 years (2014-2017) were divided into the following cohorts: Group A: Normal liver enzymes with normal CBD diameter; Group B: Normal liver enzymes with dilated CBD; Group C: Isolated rise of liver enzymes with normal CBD diameter; Group D: Isolated rise of liver enzymes with dilated CBD; Group E: Hyperbilirubinemia with normal CBD diameter; Group F: Hyperbilirubinemia with dilated CBD. Binary logistic regression models were constructed for analyses. RESULTS: Overall, 1022 patients were included. The frequency of CBDS was 7.2% in Group A; 3.8% in Group B; 6.3% in Group C; 22% in Group D; 24.2% in Group E; 47.4% in Group F. Hyperbilirubinemia with normal CBD (OR:1.52,P=0.010) and hyperbilirubinemia with dilated CBD (OR:5.12,P<0.001) independently predicted CBDS. Normal or isolated rise of liver enzymes with or without dilated CBD did not predict CBDS. Combined laboratory and ultrasonography had positive predictive value and negative predictive value of up to 47.37% and 100%, respectively. CONCLUSION: Patients with isolated rise of liver enzymes or hyperbilirubinemia with or without dilated CBD should undergo BTI prior to ERCP. Direct ERCP could be preserved for patients with high suspicion of CBDS where clinical features do not allow waiting for BTI.

Diagnostic Accuracy Of Plain X-Ray Lateral Neck In The Diagnosis Of Cervical Esophageal Foreign Bodies Keeping Oesophagoscopy As Gold Standard.

BACKGROUND: Detection of foreign body oesophagus has always been a challenge for the otolaryngologists. Among different investigations available X -ray is valuable for detection of foreign bodies as it is readily available, inexpensive and easy to operate. However, this still remains to be decided that how accurate it is? The objective of the study is to determine the diagnostic accuracy of plain X ray lateral neck in the diagnosis of foreign bodies in cervical oesophagus keeping esophagoscopy as the gold standard. METHODS: This descriptive study was conducted at department of ENT, Ayub Medical Institute (AMI) Abbottabad, from Mar to Sep 2016. A total of 290 patients were included in this study and all the patients had X-ray lateral view of neck, followed by oesophagoscopy (gold standard). Diagnostic accuracy of plain X-ray lateral view of neck was detected by determining sensitivity, specificity and accuracy. RESULTS: The sensitivity, specificity and accuracy of plain X-ray lateral view of neck was 91.7%, 80%, and 89.7%, respectively. CONCLUSIONS: X-Ray lateral view of neck is a reliable investigation and should be advised among all the patients with history of foreign body ingestion.

Impact of Toupet Versus Nissen Fundoplication on Dysphagia in Patients With Gastroesophageal Reflux Disease and Associated Preoperative Esophageal Dysmotility: A Systematic Review and Meta-Analysis.

BACKGROUND: Controversy exists regarding the best surgical approach for the management of gastroesophageal reflux disease (GORD) and associated preoperative esophageal dysmotility. Our aim was to conduct a systematic review and meta-analysis to compare the outcomes of Toupet fundoplication (TF) and Nissen fundoplication (NF) in patients with GORD and coexistent preoperative esophageal dysmotility. METHODS: We conducted a systematic search of electronic information sources, including MEDLINE, EMBASE, CINAHL, CENTRAL, ClinicalTrials.gov , and bibliographic reference lists. We applied a combination of free text search and controlled vocabulary search adapted to thesaurus headings, search operators, and limits in each of the above-mentioned databases. Postoperative dysphagia and improvement in dysphagia were primary outcome parameters. RESULTS: We identified 3 randomized controlled trials and 1 observational study reporting a total of 220 patients, of whom 126 underwent TF and the remaining 94 patients had NF. Despite the existence of significantly higher preoperative dysphagia in the TF group (29.3% vs 4.2%, P = .05), TF was associated with significantly lower postoperative dysphagia (odds ratio [OR] = 0.31, P = .002) with low between-study heterogeneity ( I2 = 11%, P = .34), and significantly higher improved dysphagia (OR = 10.32, P < .0001) with moderate between-study heterogeneity ( I2 = 31%, P = .23) compared with NF. CONCLUSION: TF may be associated with significantly lower postoperative dysphagia than NF in patients with GORD and associated preoperative esophageal dysmotility. However, no definite conclusions can be drawn as the best available evidence comes mainly from a limited number of heterogeneous randomized controlled trials. Future studies are encouraged to include patients with similar preoperative dysphagia status and report the outcomes with respect to recurrence of acid reflux symptoms.

Frequency Of Congenital Hearing Loss In Neonates.

BACKGROUND: Congenital deafness is commonest birth defect and it affects 2-4 neonates among 1000 live births. Detection and intervention especially before 6 months of age prevents severe linguistic, educational and psychosocial repercussions and helps the deaf child in the development of normal speech and language. Children who are identified after 6 months of age experience great difficulties in attaining speech and language.. METHODS: To find out the frequency of hearing loss in neonates, a hospital based observational study was conducted in Combined Military Hospital Abbottabad from June-to December 2014. One thousand new-borns selected by consecutive sampling within a specified period of time were subjected to Otoacoustic Emission (OAE) testing. Brain Evoked Response Audiometry (BERA) evaluation was performed in all those who failed OAE testing to confirm the hearing loss. Children born with microtia, meatal stenosis, cleft palate, craniofacial abnormalities and syndromic illnesses were excluded from the study. RESULTS: Of 1000 new-borns screened, 465 were males and 535 were females whereas 632 (63.2%) were delivered through C-section and 368 (36.8%) were born via SVD. Four hundred and ninety-one (49%) babies had a positive history of consanguinity among the parents. Out of 1000 infants 13 were having hearing loss which was later on confirmed on BERA evaluation. Among them 7 were males and 6 females, 9 (69%) were born through SVD and 4 (31%) through C-section and 8 (61.5%) new-borns had a positive history of consanguinity among their parents. In all these 13 patients only 2 (15%) patients had profound while the remaining 11 (85%) had moderate to severe hearing loss. CONCLUSIONS: Frequency of hearing loss in neonates is much higher in our study (13 per 1000) as compared to other parts of the world and demands that more studies should be undertaken on this subject to confirm this.

Coactivator condensation at super-enhancers links phase separation and gene control.

Super-enhancers (SEs) are clusters of enhancers that cooperatively assemble a high density of the transcriptional apparatus to drive robust expression of genes with prominent roles in cell identity. Here we demonstrate that the SE-enriched transcriptional coactivators BRD4 and MED1 form nuclear puncta at SEs that exhibit properties of liquid-like condensates and are disrupted by chemicals that perturb condensates. The intrinsically disordered regions (IDRs) of BRD4 and MED1 can form phase-separated droplets, and MED1-IDR droplets can compartmentalize and concentrate the transcription apparatus from nuclear extracts. These results support the idea that coactivators form phase-separated condensates at SEs that compartmentalize and concentrate the transcription apparatus, suggest a role for coactivator IDRs in this process, and offer insights into mechanisms involved in the control of key cell-identity genes.

Irrigation Versus Suction Alone in Laparoscopic Appendectomy: Is Dilution the Solution to Pollution? A Systematic Review and Meta-Analysis.

OBJECTIVES: To investigate outcomes of peritoneal irrigation versus suction without irrigation in patients undergoing emergency laparoscopic appendectomy. METHODS: We performed a systematic review and conducted a search of electronic information sources to identify all randomized controlled trials (RCTs) and observational studies investigating outcomes of irrigation versus suction alone in patients undergoing emergency laparoscopic appendectomy. We used the Cochrane risk of bias tool and the Newcastle-Ottawa scale to assess the risk of bias of RCTs and observational studies, respectively. Random-effects models were applied to calculate pooled outcome data. RESULTS: We identified 3 RCTs and 2 retrospective observational studies, enrolling 2511 patients. Our results suggested that there was no difference between peritoneal irrigation and suction alone in terms of intraabdominal abscess rate (odds ratio = 2.39, 95% confidence interval [CI] = 0.49-11.74, P = .28), wound infection (risk difference = 0.00, 95% CI = -0.04 to 0.05, P = .85), and length of stay (mean difference = -1.02, 95% CI = -3.10 to 1.07, P = .34); however, peritoneal irrigation was associated with longer operative time (mean difference = 7.12, 95% CI = 4.33 to 9.92, P < .00001). Our results remained consistent when randomized trials, adult patients, and pediatric patients were analyzed separately. CONCLUSIONS: The best available evidence suggests that the peritoneal irrigation with normal saline during laparoscopic appendectomy does not provide additional benefits compared with suction alone in terms of intraabdominal abscess, wound infection, and length of stay but it may prolong the operative time. The quality of the best available evidence is moderate; therefore, high-quality RCTs, which are adequately powered, are required to provide more robust basis for definite conclusions.

Stapled anastomosis versus hand-sewn anastomosis of gastro/duodenojejunostomy in pancreaticoduodenectomy: A systematic review and meta-analysis.

BACKGROUND: Controversy exists regarding the best anastomotic method for pancreaticoduodenectomy (PD). We aimed to evaluate the perioperative outcomes of PD with stapled anastomosis (SA) versus hand-sewn anastomosis (HA) of gastrojejunostomy or duodenojejunostomy. METHODS: We conducted a systematic search of electronic information sources, including MEDLINE; EMBASE; CINAHL; the Cochrane Central Register of Controlled Trials (CENTRAL); the World Health Organization International Clinical Trials Registry; ClinicalTrials.gov; ISRCTN Register, and bibliographic reference lists. We applied a combination of free text and controlled vocabulary search adapted to thesaurus headings, search operators and limits in each of the above databases. Delayed gastric emptying (DGE), postoperative pancreatic fistula (POPF), anastomotic bleeding, anastomotic leak, intra-abdominal abscess and mortality were defined as the outcome parameters. Combined overall effect sizes were calculated using fixed-effect or random-effects models. RESULTS: We identified 1 randomised controlled trial (RCT) and 5 observational studies reporting a total of 890 patients who underwent PD with SA (n = 300) or conventional HA (n = 590). Our analysis demonstrated that SA significantly reduced postoperative DGE (OR: 0.37, 95% CI 0.25-0.54, P < 0.00001) but significantly increased anastomotic bleeding (OR: 13.4, 95% CI 2.96-57.41, P = 0.0007) compared to HA. No significant difference was found in POPF (OR: 0.83, 95% CI 0.56-1.21, P = 0.33); anastomotic leak (OR: 0.50, 95% CI 0.09-3.79, P = 0.58); intra-abdominal abscess (OR: 1.39, 95% CI 0.71-2.70, P = 0.34); or mortality (RD: -0.01, 95% CI 0.03-0.02, P = 0.65) between two groups. CONCLUSIONS: Our analysis demonstrated that compared to conventional HA, SA may be associated with lower incidence of DGE after PD without increasing the risk of clinically significant POPF, anastomotic leak or mortality. However, it is associated with higher rate of anastomotic bleeding which mandates careful and precise haemostasis of the stapled line. Considering the current limited evidence, no definitive conclusion can be drawn. Future research is required.

Operative versus non-operative management of adhesive small bowel obstruction: A systematic review and meta-analysis.

OBJECTIVES: To investigate outcomes of operative and non-operative management of adhesive small bowel obstruction (SBO). METHODS: We performed a systematic review in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards. We conducted a search of electronic information sources to identify all randomised controlled trials (RCTs) and observational studies investigating outcomes of operative versus non-operative management of patients with adhesive SBO. We used the Cochrane risk of bias tool and the Newcastle-Ottawa scale to assess the risk of bias of RCTs and observational studies, respectively. Fixed-effect or random-effects models were applied to calculate pooled outcome data. RESULTS: We found one RCT, two prospective and three retrospective observational studies, enrolling a total of 876 patients. The analyses showed that operative management of adhesive SBO was associated with a lower risk of future recurrence [odds ratio (OR) 0.54, 95% confidence interval (CI) 0.38-0.76, P = 0.0005] but a higher risk of mortality [risk difference (RD) 0.03, 95% CI 0.01-0.06, P = 0.01] and complications (OR 5.39, 95% CI 2.97-9.78, P < 0.00001). There was no difference in need for surgical re-intervention rate (OR 0.72, 95% CI 0.35-1.47, P = 0.36) and length of stay [mean difference (MD) 5.07, 95% CI -2.36-12.49, P = 1.0] between operative and non-operative managements. The baseline suspicion of strangulation was a major confounding factor. When the baseline suspicion of strangulation was higher in the operative group, the risk of mortality (RD 0.04, 95% CI 0.02-0.07, P = 0.0006) and complications (OR 8.14, 95% CI 4.16-15.94, P = 0.00001) were higher in the operative group but the risk of recurrence was lower (OR 0.62, 95% CI 0.43-0.90, P = 0.01). When the baseline suspicion of strangulation was low in both groups, there was no difference in any of the outcomes except recurrence (OR 0.09, 95% CI 0.02-0.37, P = 0.0009) which was lower in the operative group. CONCLUSIONS: The difference in baseline suspicion of strangulation between operative and non-operative groups is a major confounding factor in current literature. The benefit of surgical treatment should be balanced with the risks associated with surgery, patient's co-morbidities, and presence or absence of strangulation. Based on the best available evidence it could be argued that surgical intervention could be preserved for cases with high suspicion or evidence of bowel strangulation. The controversy still remains for optimum length of conservative management and timing of surgery (early or late) for cases with low baseline suspicion of strangulation. Randomised controlled trials are required to compare outcomes of early operation (<24 h) versus late operation (>24 h) and early operation versus conservative management in patients with low suspicion of strangulation.

PIC Activation through Functional Interplay between Mediator and TFIIH.

The multiprotein Mediator coactivator complex functions in large part by controlling the formation and function of the promoter-bound preinitiation complex (PIC), which consists of RNA polymerase II and general transcription factors. However, precisely how Mediator impacts the PIC, especially post-recruitment, has remained unclear. Here, we have studied Mediator effects on basal transcription in an in vitro transcription system reconstituted from purified components. Our results reveal a close functional interplay between Mediator and TFIIH in the early stages of PIC development. We find that under conditions when TFIIH is not normally required for transcription, Mediator actually represses transcription. TFIIH, whose recruitment to the PIC is known to be facilitated by the Mediator, then acts to relieve Mediator-induced repression to generate an active form of the PIC. Gel mobility shift analyses of PICs and characterization of TFIIH preparations carrying mutant XPB translocase subunit further indicate that this relief of repression is achieved through expending energy via ATP hydrolysis, suggesting that it is coupled to TFIIH's established promoter melting activity. Our interpretation of these results is that Mediator functions as an assembly factor that facilitates PIC maturation through its various stages. Whereas the overall effect of the Mediator is to stimulate basal transcription, its initial engagement with the PIC generates a transcriptionally inert PIC intermediate, which necessitates energy expenditure to complete the process.

Mediator: A Drawbridge across the Enhancer-Promoter Divide.

Two papers in this issue of Molecular Cell provide insights into how the multisubunit Mediator coactivator complex dynamically links enhancer-bound activators to the RNA polymerase II machinery at the core promoter.