title: Specific binding sites for a pol III transcriptional repressor and pol II transcription factor YY1 within the internucleosomal spacer region in primate Alu repetitive elements.
abstract: Alu interspersed repetitive elements possess internal RNA polymerase III promoters that are transcribed in vitro and in transfected mouse cells but are nearly silent in human HeLa cells. Transcriptional repression of these elements is to some extent reversible, as pol III-dependent Alu expression can be induced with herpes simplex or adenovirus. To assess whether sequence-specific DNA binding proteins might contribute to Alu transcriptional silencing, we examined the internucleosomal spacer region surrounding the B box of the Alu pol III promoter in HeLa cell nuclei for evidence of proteins bound at specific sites in vivo. We identified a DNase I-hypersensitive site 5' to the B box and a DNase I-resistant region 3' to the B box in nuclei. An Alu-specific repressor binds to a 5-bp inverted repeat motif overlapping the 5' end of the TFIIIC binding site and may inhibit pol III transcription through competitive displacement. The level of Alu-specific pol III repressor activity is significantly reduced in adenovirus-infected HeLa cells, suggesting that the repressor may contribute to Alu transcriptional silencing in vivo. The 3' DNase I-resistant region coincided with a binding site for the pol II transcription factor YY1 in vitro. YY1 is one of the major proteins in HeLa cells having binding specificity for Alu elements. YY1 bound to tandem arrays of genomic Alu elements may play a role in chromatin organization and silencing.
authors.affiliation: Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: G W
authors.initials: GW
authors.lastname: Humphrey
authors.forename: E W
authors.initials: EW
authors.lastname: Englander
authors.forename: B H
authors.initials: BH
authors.lastname: Howard
mesh_terms: D000256:Adenoviridae; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050981:Erythroid-Specific DNA-Binding Factors; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism*; D012320:RNA Polymerase III / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000032:analysis / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D050986:YY1 Transcription Factor; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D050986:YY1 Transcription Factor; C494698:YY1 protein, human; C494699:Yy1 protein, mouse; D012319:RNA Polymerase II; D012320:RNA Polymerase III