技术资料

BACKGROUND {\&} AIMS RNase H2 is a holoenzyme,composed of 3 subunits (ribonuclease H2 subunits A,B,and C),that cleaves RNA:DNA hybrids and removes mis-incorporated ribonucleotides from genomic DNA through ribonucleotide excision repair. Ribonucleotide incorporation by eukaryotic DNA polymerases occurs during every round of genome duplication and produces the most frequent type of naturally occurring DNA lesion. We investigated whether intestinal epithelial proliferation requires RNase H2 function and whether RNase H2 activity is disrupted during intestinal carcinogenesis. METHODS We generated mice with epithelial-specific deletion of ribonuclease H2 subunit B (H2b$\Delta$IEC) and mice that also had deletion of tumor-suppressor protein p53 (H2b/p53$\Delta$IEC); we compared phenotypes with those of littermate H2bfl/fl or H2b/p53fl/fl (control) mice at young and old ages. Intestinal tissues were collected and analyzed by histology. We isolated epithelial cells,generated intestinal organoids,and performed RNA sequence analyses. Mutation signatures of spontaneous tumors from H2b/p53$\Delta$IEC mice were characterized by exome sequencing. We collected colorectal tumor specimens from 467 patients,measured levels of ribonuclease H2 subunit B,and associated these with patient survival times and transcriptome data. RESULTS The H2b$\Delta$IEC mice had DNA damage to intestinal epithelial cells and proliferative exhaustion of the intestinal stem cell compartment compared with controls and H2b/p53$\Delta$IEC mice. However,H2b/p53$\Delta$IEC mice spontaneously developed small intestine and colon carcinomas. DNA from these tumors contained T{\textgreater}G base substitutions at GTG trinucleotides. Analyses of transcriptomes of human colorectal tumors associated lower levels of RNase H2 with shorter survival times. CONCLUSIONS In analyses of mice with disruption of the ribonuclease H2 subunit B gene and colorectal tumors from patients,we provide evidence that RNase H2 functions as a colorectal tumor suppressor. H2b/p53$\Delta$IEC mice can be used to study the roles of RNase H2 in tissue-specific carcinogenesis. View Publication

A coding variant of the inflammatory bowel disease (IBD) risk gene ATG16L1 has been associated with defective autophagy and deregulation of endoplasmic reticulum (ER) function. IL-22 is a barrier protective cytokine by inducing regeneration and antimicrobial responses in the intestinal mucosa. We show that ATG16L1 critically orchestrates IL-22 signaling in the intestinal epithelium. IL-22 stimulation physiologically leads to transient ER stress and subsequent activation of STING-dependent type I interferon (IFN-I) signaling,which is augmented in Atg16l1$\Delta$IEC intestinal organoids. IFN-I signals amplify epithelial TNF production downstream of IL-22 and contribute to necroptotic cell death. In vivo,IL-22 treatment in Atg16l1$\Delta$IEC and Atg16l1$\Delta$IEC/Xbp1$\Delta$IEC mice potentiates endogenous ileal inflammation and causes widespread necroptotic epithelial cell death. Therapeutic blockade of IFN-I signaling ameliorates IL-22-induced ileal inflammation in Atg16l1$\Delta$IEC mice. Our data demonstrate an unexpected role of ATG16L1 in coordinating the outcome of IL-22 signaling in the intestinal epithelium. View Publication