Enhancement of the transcription potential of nascent chromatin by chromosomal proteins HMG-14/-17 is coupled to nucleosome assembly and not DNA synthesis.
We have previously demonstrated that in Xenopus egg extracts, which support DNA strand synthesis and chromatin assembly, incorporation of chromosomal proteins HMG-14/-17 into nascent nucleosomes increases the transcriptional potential of a chromatin template carrying the Xenopus 5S RNA gene. Here we use the single-stranded and double-stranded forms of a plasmid carrying a 5S RNA maxigene, to test whether the effect of HMG-14/-17 on transcription requires DNA synthesis and whether these proteins will affect transcription through a region containing nucleosomes. We find that most of the transcripts were about 350 nucleotides long, suggesting that HMG-14/-17 enhance transcription through a region that could contain nucleosomes. HMG-14/-17 enhance transcription of chromatin templates assembled onto double-stranded DNA, in the absence of DNA synthesis. Single-round transcription assays suggest that HMG-14/-17 increase transcription from templates assembled onto both single- and double-stranded DNA by increasing the specific activity, and not the number, of transcriptionally active templates. We conclude that the effect of HMG-14/-17 on the transcriptional potential of chromatin is linked to nucleosome assembly and is not linked to DNA synthesis.
Weigmann
N
N
Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Trieschmann
L
L
Bustin
M
M
D000818:Animals; D002843:Chromatin / Q000235:genetics; D004247:DNA / Q000096:biosynthesis*; D004277:DNA, Single-Stranded / Q000096:biosynthesis; D006609:High Mobility Group Proteins / Q000502:physiology*; D009707:Nucleosomes / Q000378:metabolism*; D010063:Ovum; D010957:Plasmids / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D013698:Templates, Genetic; D014158:Transcription, Genetic / Q000502:physiology*; D014981:Xenopus / Q000235:genetics; D014982:Xenopus laevis
D002843:Chromatin; D004277:DNA, Single-Stranded; D006609:High Mobility Group Proteins; D009707:Nucleosomes; D012333:RNA, Messenger; D012341:RNA, Ribosomal, 5S; D004247:DNA