In vivo structure of two divergent promoters at the human PCNA locus. Synthesis of antisense RNA and S phase-dependent binding of E2F complexes in intron 1.
Proliferating cell nuclear antigen (PCNA) synthesis is strictly regulated during the cell cycle. To investigate PCNA transcriptional regulation, we have analyzed protein-DNA interactions at the promoter region and in the first intron in quiescent fibroblasts and following serum stimulation. Twenty putative protein-binding sites, distributed in two divergent promoters at the PCNA locus, were identified in vivo by genomic footprinting. These elements bind transcription factors continuously throughout the cell cycle with the exception of one E2F consensus site, located in the first intron at position +583. This E2F site becomes strongly occupied 18 h after serum stimulation, implying that an E2F activator complex plays a role in activation of the PCNA gene at the onset of S phase. We detected a 500-600-base pair-long antisense transcript by Northern blot analysis. This RNA has no apparent coding capacity and is constitutively transcribed from a promoter located within the first intron. We suggest that silencing of the PCNA gene is accomplished through base pairing between sense pre-mRNA and antisense RNA. The binding of S phase-specific E2F complexes at the +583 element may help to overcome the negative effect of the antisense transcript, which results in up-regulation of PCNA expression in proliferating cells.
Tommasi
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Department of Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California 91010, USA. stomassi@smtplink.coh.org
Pfeifer
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D020029:Base Pairing; D001483:Base Sequence; D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D018983:DNA Footprinting; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D005091:Exons; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation; D014644:Genetic Variation; D006801:Humans; D007438:Introns; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D016372:RNA, Antisense / Q000235:genetics* / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase; D016415:Sequence Alignment; D012867:Skin / Q000166:cytology / Q000378:metabolism; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D018809:Proliferating Cell Nuclear Antigen; D012322:RNA Precursors; D016372:RNA, Antisense; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors