title: A downstream CpG island controls transcript initiation and elongation and the methylation state of the imprinted Airn macro ncRNA promoter.
abstract: A CpG island (CGI) lies at the 5' end of the Airn macro non-protein-coding (nc) RNA that represses the flanking Igf2r promoter in cis on paternally inherited chromosomes. In addition to being modified on maternally inherited chromosomes by a DNA methylation imprint, the Airn CGI shows two unusual organization features: its position immediately downstream of the Airn promoter and transcription start site and a series of tandem direct repeats (TDRs) occupying its second half. The physical separation of the Airn promoter from the CGI provides a model to investigate if the CGI plays distinct transcriptional and epigenetic roles. We used homologous recombination to generate embryonic stem cells carrying deletions at the endogenous locus of the entire CGI or just the TDRs. The deleted Airn alleles were analyzed by using an ES cell imprinting model that recapitulates the onset of Igf2r imprinted expression in embryonic development or by using knock-out mice. The results show that the CGI is required for efficient Airn initiation and to maintain the unmethylated state of the Airn promoter, which are both necessary for Igf2r repression on the paternal chromosome. The TDRs occupying the second half of the CGI play a minor role in Airn transcriptional elongation or processivity, but are essential for methylation on the maternal Airn promoter that is necessary for Igf2r to be expressed from this chromosome. Together the data indicate the existence of a class of regulatory CGIs in the mammalian genome that act downstream of the promoter and transcription start.
authors.affiliation: CeMM-Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.
authors.forename: Martha V
authors.initials: MV
authors.lastname: Koerner
authors.forename: Florian M
authors.initials: FM
authors.lastname: Pauler
authors.forename: Quanah J
authors.initials: QJ
authors.lastname: Hudson
authors.forename: Federica
authors.initials: F
authors.lastname: Santoro
authors.forename: Anna
authors.initials: A
authors.lastname: Sawicka
authors.forename: Philipp M
authors.initials: PM
authors.lastname: Guenzl
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Stricker
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Schichl
authors.forename: Paulina A
authors.initials: PA
authors.lastname: Latos
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Klement
authors.forename: Katarzyna E
authors.initials: KE
authors.lastname: Warczok
authors.forename: Jacek
authors.initials: J
authors.lastname: Wojciechowski
authors.forename: Christian
authors.initials: C
authors.lastname: Seiser
authors.forename: Robert
authors.initials: R
authors.lastname: Kralovics
authors.forename: Denise P
authors.initials: DP
authors.lastname: Barlow
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D047108:Embryonic Development; D053595:Embryonic Stem Cells; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D018392:Genomic Imprinting; D059765:Homologous Recombination; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011401:Promoter Regions, Genetic; D012322:RNA Precursors / Q000235:genetics*; D022661:RNA, Untranslated / Q000235:genetics*; D017384:Sequence Deletion; D020080:Tandem Repeat Sequences; D024363:Transcription Initiation Site
chemical_list: C513121:IGF2 protein, mouse; D012322:RNA Precursors; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II