title: RFTS-deleted DNMT1 enhances tumorigenicity with focal hypermethylation and global hypomethylation.
abstract: Site-specific hypermethylation of tumor suppressor genes accompanied by genome-wide hypomethylation are epigenetic hallmarks of malignancy. However, the molecular mechanisms that drive these linked changes in DNA methylation remain obscure. DNA methyltransferase 1 (DNMT1), the principle enzyme responsible for maintaining methylation patterns is commonly dysregulated in tumors. Replication foci targeting sequence (RFTS) is an N-terminal domain of DNMT1 that inhibits DNA-binding and catalytic activity, suggesting that RFTS deletion would result in a gain of DNMT1 function. However, a substantial body of data suggested that RFTS is required for DNMT1 activity. Here, we demonstrate that deletion of RFTS alters DNMT1-dependent DNA methylation during malignant transformation. Compared to full-length DNMT1, ectopic expression of hyperactive DNMT1-ΔRFTS caused greater malignant transformation and enhanced promoter methylation with condensed chromatin structure that silenced DAPK and DUOX1 expression. Simultaneously, deletion of RFTS impaired DNMT1 chromatin association with pericentromeric Satellite 2 (SAT2) repeat sequences and produced DNA demethylation at SAT2 repeats and globally. To our knowledge, RFTS-deleted DNMT1 is the first single factor that can reprogram focal hypermethylation and global hypomethylation in parallel during malignant transformation. Our evidence suggests that the RFTS domain of DNMT1 is a target responsible for epigenetic changes in cancer.
authors.affiliation: a Department of Biochemistry; Carver College of Medicine ; University of Iowa ; Iowa City , IA USA.
authors.forename: Bo-Kuan
authors.initials: BK
authors.lastname: Wu
authors.forename: Szu-Chieh
authors.initials: SC
authors.lastname: Mei
authors.forename: Charles
authors.initials: C
authors.lastname: Brenner
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D047369:Chromatin Immunoprecipitation; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation / Q000235:genetics / Q000502:physiology; D006801:Humans; D015151:Immunoblotting
chemical_list: D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human
keywords: COSMIC, catalog of somatic mutation in cancer; DNA methylation; DNMT1; DNMT1, DNA methyltransferase 1; HELP, HpaII tiny fragment enrichment by ligation-mediated PCR; KEGG, Kyoto Encyclopedia of Genes and Genomes; RFTS domain; RFTS, replication foci targeting sequence; TSGs, tumor suppressor genes; chromatin; tumorigenicity