title: ICF syndrome mutations cause a broad spectrum of biochemical defects in DNMT3B-mediated de novo DNA methylation.
abstract: The DNMT3B de novo DNA methyltransferase (DNMT) plays a major role in establishing DNA methylation patterns in early mammalian development, but its catalytic mechanism remains poorly characterized. Here, we provide a comprehensive biochemical analysis of human DNMT3B function through the characterization of a series of site-directed DNMT3B variants associated with immunodeficiency, centromere instability, and facial anomalies (ICF) syndrome. Our data reveal several novel and important aspects of DNMT3B function. First, DNMT3B, unlike DNMT3A, requires a DNA cofactor in order to stably bind to S-adenosyl-l-methionine (SAM), suggesting that it proceeds according to an ordered catalytic scheme. Second, ICF mutations cause a broad spectrum of biochemical defects in DNMT3B function, including defects in homo-oligomerization, SAM binding, SAM utilization, and DNA binding. Third, all tested ICF mutations, including the A766P and R840Q variants, result in altered catalytic properties without interfering with DNMT3L-mediated stimulation; this indicates that DNMT3L is not involved in the pathogenesis of ICF syndrome. Finally, our study reveals a novel level of coupling between substrate binding, oligomerization, and catalysis that is likely conserved within the DNMT3 family of enzymes.
authors.affiliation: Department of Molecular and Cellular Biology, One Shields Avenue, Briggs Hall, University of California, Davis, CA 95616, USA.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Moarefi
authors.forename: Frédéric
authors.initials: F
authors.lastname: Chédin
mesh_terms: D002384:Catalysis; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D019175:DNA Methylation; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D013577:Syndrome; D000097584:DNA Methyltransferase 3B
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases; D000097584:DNA Methyltransferase 3B