title: Nonallelic transcriptional roles of CTCF and cohesins at imprinted loci.
abstract: The cohesin complex holds sister chromatids together and is essential for chromosome segregation. Recently, cohesins have been implicated in transcriptional regulation and insulation through genome-wide colocalization with the insulator protein CTCF, including involvement at the imprinted H19/Igf2 locus. CTCF binds to multiple imprinted loci and is required for proper imprinted expression at the H19/Igf2 locus. Here we report that cohesins colocalize with CTCF at two additional imprinted loci, the Dlk1-Dio3 and the Kcnq1/Kcnq1ot1 loci. Similar to the H19/Igf2 locus, CTCF and cohesins preferentially bind to the Gtl2 differentially methylated region (DMR) on the unmethylated maternal allele. To determine the functional importance of the binding of CTCF and cohesins at the three imprinted loci, CTCF and cohesins were depleted in mouse embryonic fibroblast cells. The monoallelic expression of imprinted genes at these three loci was maintained. However, mRNA levels for these genes were typically increased; for H19 and Igf2 the increased level of expression was independent of the CTCF-binding sites in the imprinting control region. Results of these experiments demonstrate an unappreciated role for CTCF and cohesins in the repression of imprinted genes in somatic cells.
authors.affiliation: Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Lin
authors.forename: Anne C
authors.initials: AC
authors.lastname: Ferguson-Smith
authors.forename: Richard M
authors.initials: RM
authors.lastname: Schultz
authors.forename: Marisa S
authors.initials: MS
authors.lastname: Bartolomei
mesh_terms: D000818:Animals; D000076246:CCCTC-Binding Factor; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D002842:Chromatids / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D020090:Chromosome Segregation; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts; D015870:Gene Expression; D005786:Gene Expression Regulation; D020868:Gene Silencing; D005809:Genes, Regulator; D018392:Genomic Imprinting; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D062085:RNA, Long Noncoding; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D000097722:Cohesins
chemical_list: D000076246:CCCTC-Binding Factor; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D007335:Insulin-Like Growth Factor II; D036341:Intercellular Signaling Peptides and Proteins; D051657:KCNQ1 Potassium Channel; D011506:Proteins; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D012097:Repressor Proteins; D000097722:Cohesins; C000619698:Ctcf protein, mouse; C512925:Dlk1 protein, mouse; C094335:H19 long non-coding RNA; C513121:IGF2 protein, mouse; C422882:MEG3 non-coding RNA, mouse