A conserved 3'-untranslated element mediates growth regulation of DNA methyltransferase 1 and inhibits its transforming activity.
Ectopic expression of DNA methyltransferase 1 (DNMT1) has been proposed to play an important role in cancer. dnmt1 mRNA is undetectable in growth-arrested cells but is induced upon entrance into the S phase of the cell cycle, and until now, the mechanisms responsible for this regulation were unknown. In this report, we demonstrate that the 3'-untranslated region (3'-UTR) of the dnmt1 mRNA can confer a growth-dependent regulation on its own message as well as a heterologous beta-globin mRNA. Our results indicate that a 54-nucleotide highly conserved element within the 3'-UTR is necessary and sufficient to mediate this regulation. Cell-free mRNA decay experiments demonstrate that this element increases mRNA turnover rates and does so to a greater extent in the presence of extracts prepared from arrested cells. A specific RNA-protein complex is formed with the 3'-UTR only in growth-arrested cells, and a UV cross-linking analysis revealed a 40-kDa protein (p40), the binding of which is dramatically increased in growth-arrested cells and is inversely correlated with dnmt1 mRNA levels as cells are induced into the cell cycle. Although ectopic expression of human DNMT1 lacking the 3'-UTR can transform NIH-3T3 cells, inclusion of the 3'-UTR prevents transformation. These results support the hypothesis that deregulated expression of DNMT1 with the cell cycle is important for cellular transformation.
Detich
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N
Department of Pharmacology and Therapeutics, McGill University, 3655 Sir William Osler Promenade, Montreal, Quebec H3G 1Y6, Canada.
Ramchandani
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S
Szyf
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M
D020413:3' Untranslated Regions / Q000502:physiology*; D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D002471:Cell Transformation, Neoplastic; D002645:Chickens; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015536:Down-Regulation; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014162:Transfection; D014981:Xenopus
D020413:3' Untranslated Regions; D012333:RNA, Messenger; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; C000619382:Dnmt1 protein, rat