title: Active repression of methylated genes by the chromosomal protein MBD1.
abstract: MBD1 belongs to a family of mammalian proteins that share a methyl-CpG binding domain. Previous work has shown that MBD1 binds to methylated sites in vivo and in vitro and can repress transcription from methylated templates in transcription extracts and in cultured cells. In the present study we established by several experimental criteria that, contrary to a previous report, MBD1 is not a component of the MeCP1 repressor complex. We identified a powerful transcriptional repression domain (TRD) at the C terminus of MBD1 that can actively repress transcription at a distance. Methylation-dependent repression in vivo depends on the presence of both the TRD and the methyl-CpG binding domain. The mechanism is likely to involve deacetylation, since the deacetylase inhibitor trichostatin A can overcome MBD1-mediated repression. Accordingly, we found that endogenous MBD1 is particularly concentrated at sites of centromeric heterochromatin, where acetylated histone H4 is deficient. Unlike MBD2 and MeCP2, MBD1 is not depleted by antibodies to the histone deacetylase HDAC1. Thus, the deacetylase-dependent pathway by which MBD1 actively silences methylated genes is likely to be different from that utilized by the methylation-dependent repressors MeCP1 and MeCP2.
authors.affiliation: Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.
authors.forename: H H
authors.initials: HH
authors.lastname: Ng
authors.forename: P
authors.initials: P
authors.lastname: Jeppesen
authors.forename: A
authors.initials: A
authors.lastname: Bird
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002877:Chromosomes, Human / Q000378:metabolism; D018899:CpG Islands; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D056284:Histone Deacetylase 1; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056572:Histone Deacetylase Inhibitors; C066141:MBD1 protein, human; C489325:MBD2 protein, human; C489323:Mbd1 protein, mouse; C489324:Mbd1 protein, rat; C489689:MeCP1 histone deacetylase complex, human; C489690:MeCP1 histone deacetylase complex, mouse; D012097:Repressor Proteins; D014157:Transcription Factors; D004247:DNA; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases