Elongation and premature termination of transcripts initiated from c-fos and c-myc promoters show dissimilar patterns.
RNA polymerase II seems to be prone to stop at intrinsic pause sites, thus introducing a further potential level of regulation. It was recently shown that RNA polymerase II was held at the P2 promoter of c-myc gene. We confirmed the presence of engaged polymerases in the murine fibroblastic Ltk- and pre-B lymphoid 70Z3 cell lines. High resolution run-on analysis and in vivo permanganate-dependent footprinting showed that this holds true for the c-fos gene in unstimulated cells where a strong block to transcription elongation was evidenced. In contrast to what was observed in the c-myc gene, an even more intense signal was observed in run-on experiments downstream to the promoter, on a c-fos oligonucleotide including position +385 where an in vitro transcription arrest site was previously mapped. Genomic footprinting of DNA from intact cells and isolated nuclei confirmed the involvement of several thymidines belonging to a T-rich stretch in a melted region which was not detected upon polymerase release. In order to observe a short abortive c-fos transcript accumulating in vivo we resorted to microinjection of c-fos templates in Xenopus oocytes where transcripts were stable.
Institut de Génétique Moléculaire de Montpellier UMR 9942, CNRS, France.
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Eick
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Blanchard
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D005347:Fibroblasts; D005786:Gene Expression Regulation; D016762:Genes, fos; D016259:Genes, myc; D051379:Mice; D008969:Molecular Sequence Data; D010441:Peptide Chain Elongation, Translational; D010443:Peptide Chain Termination, Translational; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000502:physiology*; D014162:Transfection; D014981:Xenopus / Q000235:genetics
D012319:RNA Polymerase II