The transcription complex of the 5 S RNA gene, but not transcription factor IIIA alone, prevents nucleosomal repression of transcription.
Assembly of nucleosomes on a 5 S DNA plasmid with histone H3.H4-N1 complex and histone H2A-H2B dimers causes a marked, 30-300-fold repression of 5 S RNA transcription. This repression is a time-dependent process that parallels the process of nucleosome formation. At physiological histone levels, DNA plasmids carrying nucleosomes with only histones H3 and H4 are transcriptionally permissive. The histone H3-H4 chromatin becomes transcriptionally nonpermissive when histone H2A-H2B dimers complement the nucleosome assembly reaction. H3-H4-H2A-H2B nucleosomes, but not H3-H4 nucleosomes, displace a DNA-bound transcription factor IIIA. In contrast, a preassembled 5 S RNA transcription complex is refractory to inactivation by nucleosomes.
Tremethick
D
D
Department of Biology, University of Rochester, New York 14627.
Zucker
K
K
Worcel
A
A
D000818:Animals; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I; D005260:Female; D006657:Histones / Q000378:metabolism; D046911:Macromolecular Substances; D009707:Nucleosomes / Q000378:metabolism*; D009710:Nucleotide Mapping; D009865:Oocytes / Q000378:metabolism; D010957:Plasmids; D012320:RNA Polymerase III / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics*; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014982:Xenopus laevis
D004275:DNA, Ribosomal; D006657:Histones; D046911:Macromolecular Substances; D009707:Nucleosomes; D012335:RNA, Ribosomal; D012341:RNA, Ribosomal, 5S; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D012320:RNA Polymerase III; D003850:Deoxyribonuclease I