Summary Covalent addition of a methyl group to the adenosine N6 (m6A) is an evolutionarily conserved and common RNA modification that is thought to modulate several aspects of RNA metabolism. While the presence of multiple m6A editing sites on diverse viral RNAs was reported starting almost 40 years ago, how m6A editing affects virus replication has remained unclear. Here, we used photo-crosslinking-assisted m6A sequencing techniques to precisely map several m6A editing sites on the HIV-1 genome and report that they cluster in the HIV-1 3’ untranslated region (3'UTR). Viral 3'UTR m6A sites or analogous cellular m6A sites strongly enhanced mRNA expression in cis by recruiting the cellular YTHDF m6A “reader” proteins. Reducing YTHDF expression inhibited, while YTHDF overexpression enhanced, HIV-1 protein and RNA expression, and virus replication in CD4+ T cells. These data identify m6A editing, and the resultant recruitment of YTHDF proteins, as major positive regulators of HIV-1 mRNA expression.

5-Fluorouracil (5-FU) remains the first-line treatment for colorectal cancer (CRC). Although 5-FU initially de-bulks the tumor mass, recurrence after chemotherapy is the barrier to effective clinical outcomes for CRC patients. Here, we demonstrate that p53 promotes WNT3 transcription, leading to activation of the WNT/β-catenin pathway in ApcMin/+/Lgr5EGFP mice, CRC patient-derived tumor organoids (PDTOs) and patient-derived tumor cells (PDCs). Through this regulation, 5-FU induces activation and enrichment of cancer stem cells (CSCs) in the residual tumors, contributing to recurrence after treatment. Combinatorial treatment of a WNT inhibitor and 5-FU effectively suppresses the CSCs and reduces tumor regrowth after discontinuation of treatment. These findings indicate p53 as a critical mediator of 5-FU-induced CSC activation via the WNT/β-catenin signaling pathway and highlight the significance of combinatorial treatment of WNT inhibitor and 5-FU as a compelling therapeutic strategy to improve the poor outcomes of current 5-FU-based therapies for CRC patients.

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We purified to homogeneity an enzyme from Citrobacter sp. strain KCTC 18061P capable of decolorizing triphenylmethane dyes. The native form of the enzyme was identified as a homodimer with a subunit molecular mass of about 31 kDa. It catalyzes the NADH-dependent reduction of triphenylmethane dyes, with remarkable substrate specificity related to dye structure. Maximal enzyme activity occurred at pH 9.0 and 60°C. The enzymatic reaction product of the triphenylmethane dye crystal violet was identified as its leuco form by UV-visible spectral changes and thin-layer chromatography. A gene encoding this enzyme was isolated based on its N-terminal and internal amino acid sequences. The nucleotide sequence of the gene has a single open reading frame encoding 287 amino acids with a predicted molecular mass of 30,954 Da. Although the deduced amino acid sequence displays 99% identity to the hypothetical protein from Listeria monocytogenes strain 4b H7858, it shows no overall functional similarity to any known protein in the public databases. At the N terminus, the amino acid sequence has high homology to sequences of NAD(P)H-dependent enzymes containing the dinucleotide-binding motif GXXGXXG. The enzyme was heterologously expressed in Escherichia coli, and the purified recombinant enzyme showed characteristics similar to those of the native enzyme. This is the first report of a triphenylmethane reductase characterized from any organism.Triphenylmethane dyes are aromatic xenobiotic compounds that are used extensively in many industrial processes, such as textile dyeing, paper printing, and food and cosmetic manufacture (11). Studies of the biodegradation of triphenylmethane dyes have focused primarily on the decolorization of dyes via reduction reactions. Several triphenylmethane dye-decolorizing microorganisms have been reported and their characteristics reviewed (2). The biochemical mechanism underlying the decolorization of triphenylmethane dyes has been elucidated in fungi (2,7,20,23) but not in bacteria. Triphenylmethane dyes are decolorized by lignin peroxidase of Phanerochaete chrysosporium (7). Laccase from the extracellular fluid of Cyathus bulleri (23) and peroxidase from Pleurotus ostreatus (20) also decolorize triphenylmethane dyes. The structural genes encoding lignin peroxidase and laccase have been cloned and characterized (8, 10). Although several triphenylmethane dye-decolorizing bacteria have been isolated (2), there are no reports of specific enzymes that decolorize these dyes. The decolorization of malachite green and crystal violet by intestinal microflora and several anaerobic bacteria proceeds through enzymatic reduction to their respective leuco derivatives (12, 16). However, the enzymes involved in this reduction have not yet been isolated or characterized in their purified forms. Their amino acid sequences and other biophysical parameters remain unknown.We recently isolated a new bacterium, Citrobacter sp. strain KCTC 18061P, that has a higher decolorization capability than any microorganism repor...

Epstein-Barr virus (EBV) is a ubiquitous human γ-herpesvirus that can give rise to cancers of both B-cell and epithelial cell origin. In EBV-induced cancers of epithelial origin, including nasopharyngeal carcinomas (NPCs) and gastric carcinomas, the latent EBV genome expresses very high levels of a cluster of 22 viral pre-miRNAs, called the miR-BARTs, and these have previously been shown to confer a degree of resistance to pro-apoptotic drugs. Here, we present an analysis of the ability of individual miR-BART pre-miRNAs to confer an anti-apoptotic phenotype and report that five of the 22 miR-BARTs demonstrate this ability. We next used photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) to globally identify the mRNA targets bound by these miR-BARTs in latently infected epithelial cells. This led to the identification of ten mRNAs encoding pro-apoptotic mRNA targets, all of which could be confirmed as valid targets for the five anti-apoptotic miR-BARTs by indicator assays and by demonstrating that ectopic expression of physiological levels of the relevant miR-BART in the epithelial cell line AGS resulted in a significant repression of the target mRNA as well as the encoded protein product. Using RNA interference, we further demonstrated that knockdown of at least seven of these cellular miR-BART target transcripts phenocopies the anti-apoptotic activity seen upon expression of the relevant EBV miR-BART miRNA. Together, these observations validate previously published reports arguing that the miR-BARTs can exert an anti-apoptotic effect in EBV-infected epithelial cells and provide a mechanistic explanation for this activity. Moreover, these results identify and validate a substantial number of novel mRNA targets for the anti-apoptotic miR-BARTs.

Despite its importance in cell proliferation and tumorigenesis, very little is known about the molecular mechanism underlying the regulation of phospholipase D (PLD) expression. PLD isozymes are significantly co-overexpressed with cancer marker genes in colorectal carcinoma. Phorbol 12-myristate 13-acetate (PMA) treatment, as a mitogenic signal in colon cancer cells, selectively increases PLD1 expression in transcription and posttranscription. Moreover, experiments using intraperitoneal injection of PMA into mice showed selective PLD1 induction in the intestine and lung tissues, which suggests its physiological relevance in vivo. Therefore, we have undertaken a detailed analysis of the effects of PMA on the promoter activity of PLD genes. Protein kinase C inhibitors, but not a protein kinase A inhibitor, were found to suppress the up-regulation of PLD1 but not PLD2. Dominant-negative mutants of Ras, Raf, and MEK suppressed the induction and activity of PLD1. Moreover, depletion of the supposedly involved proteins reduced the endogenous PLD1 protein level. An important role for NFB as a downstream target of ERK in PMA-induced PLD1 induction was also demonstrated using the inhibitor, small interfering RNA, chromatin immunoprecipitation assay, and site-specific mutagenesis. Furthermore, inhibitors of these signaling proteins and depletion of PLD1 suppressed PMA-induced matrix metalloproteinase-9 secretion and PLD1 induction. In conclusion, we demonstrate for the first time that induction of PLD1 through a protein kinase C/Ras/ERK/NFB-dependent pathway is involved in the secretion of matrix metalloproteinase-9 in colorectal cancer cells.

BACKGROUND: Robotic total mesorectal excision for rectal cancer has rapidly increased and has shown short-term outcomes comparable to conventional laparoscopic total mesorectal excision. However, data for long-term oncologic outcomes are limited. OBJECTIVE: The aim of this study is to evaluate long-term oncologic outcomes of robotic total mesorectal excision compared with laparoscopic total mesorectal excision. DESIGN: This was a retrospective study. SETTINGS: This study was conducted in a tertiary referral hospital. PATIENTS: A total of 732 patients who underwent totally robotic (n = 272) and laparoscopic (n = 460) total mesorectal excision for rectal cancer were included in this study. MAIN OUTCOME MEASURES: We compared clinicopathologic outcomes of patients. In addition, short- and long-term outcomes and prognostic factors for survival were evaluated in the matched robotic and laparoscopic total mesorectal excision groups (224 matched pairs by propensity score). RESULTS: Before case matching, patients in the robotic group were younger, more likely to have undergone preoperative chemoradiation, and had a lower tumor location than those in the laparoscopic group. After case matching most clinicopathologic outcomes were similar between the groups, but operative time was longer and postoperative ileus was more frequent in the robotic group. In the matched patients excluding stage IV, the overall survival, cancer-specific survival, and disease-free survival were better in the robotic group, but did not reach statistical significance. The 5-year survival rates for robotic and laparoscopic total mesorectal excision were 90.5% and 78.0% for overall survival, 90.5% and 79.5% for cancer-specific survival, and 72.6% and 68.0% for disease-free survival. In multivariate analysis, robotic surgery was a significant prognostic factor for overall survival and cancer-specific survival (p = 0.0040, HR = 0.333; p = 0.0161, HR = 0.367). LIMITATIONS: This study has the potential for selection bias and limited generalizability. CONCLUSIONS: Robotic total mesorectal excision for rectal cancer showed long-term survival comparable to laparoscopic total mesorectal excision in this study. Robotic surgery was a good prognostic factor for overall survival and cancer-specific survival, suggesting potential oncologic benefits.

Kang et al. show that genetic or pharmacological inactivation of the enzyme phospholipase D1 (PLD1) disrupts colitis-associated intestinal tumorigenesis by suppressing the self-renewal capacity of colon cancer stem cells.