The CCCTC-binding factor CTCF represses hepatitis B virus enhancer I and regulates viral transcription

Hepatitis B virus (HBV) infection is of global importance with over 2 billion people exposed to the virus during their lifetime and at risk of progressive liver disease, cirrhosis and hepatocellular carcinoma. HBV is a member of the Hepadnaviridae family that replicates via episomal copies of a covalently closed circular DNA (cccDNA) genome. The chromatinization of this small viral genome, with overlapping open reading frames and regulatory elements, suggests an important role for epigenetic pathways to regulate viral transcription. The chromatin-organising transcriptional insulator protein, CCCTC-binding factor (CTCF), has been reported to regulate transcription in a diverse range of viruses. We identified two conserved CTCF binding sites in the HBV genome within enhancer I and chromatin immunoprecipitation (ChIP) analysis demonstrated an enrichment of CTCF binding to integrated or episomal copies of the viral genome. siRNA knock-down of CTCF results in a significant increase in pre-genomic RNA levels in de novo infected HepG2 cells and those supporting episomal HBV DNA replication. Furthermore, mutation of these sites in HBV DNA minicircles abrogated CTCF binding and increased pre-genomic RNA levels, providing evidence of a direct role for CTCF in repressing HBV transcription.

Outcomes Of Patients with Delayed Surveillance Colonoscopy

BACKGROUND

Surveillance colonoscopy has been shown to be an effective tool for prevention of CRC in high-risk populations, if adhered to. We aimed to discover the sequelae of late surveillance in a cohort of patient's overdue for colonoscopy, in particular the development of colorectal cancer (CRC) or advanced adenoma (AA) within surveillance subgroups.

METHOD

We conducted a retrospective cohort study on all patients from the Bay of Plenty District Health Board region, New Zealand, placed on the colonoscopy surveillance waitlist from 2006 onwards who had their procedure completed between 1 November 2016 and 31 January 2018, when the total surveillance list was declared up-to-date. Patients with overdue surveillance, defined as done later than 90 days after the recommended due date were compared to patients who were done either early, or on time.

RESULTS

786 patients were recorded as overdue for surveillance colonoscopy, and 386 were completed early or on time. The median time overdue was 22 months. Three cases (0.4%) of CRC were found in overdue patients compared to 4 cases (1%) for those done on time (adjusted p=0.24). There were 86 (11%) AA in patient's overdue compared to 27 (7%) in those not overdue (odds ratio (OR) 1.6, 95% confidence interval (CI) [1.0,2.5], p=0.04). Overdue status increased the expected risk of AA by approximately 60% (adjusted; 95% CI [1%,253%], p=0.04) or 19% per year overdue (95% CI [7%,32%], p=0.002). Surveillance of 248 low-risk post-polypectomy patients demonstrated 26/211 with AA in overdue patients compared to 2/37 (12.3% vs 5.4%, unadjusted p=0.23) for those done on time. Surveillance of 180 high-risk post-polypectomy patients identified 2 CRC's and 8/43 AA in those overdue, as compared to no CRC and 9/137 AA (18.6% vs 6.6%, OR 1.79 (95% CI [1.07,2.0], unadjusted p=0.03) in those done on time.

CONCLUSION

Whilst overdue surveillance is not predictive of increased CRC, it is associated with an increase in expected number of AA, particularly in patients having surveillance for previous high-risk polypectomy. This article is protected by copyright. All rights reserved.