Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies on a chromatin reporter gene (GAL-URARIB) in yeast showed that nucleosomes were maintained but rearranged during transcription in galactose, which was consistent with local dissociation of histones at the site of the RNA polymerase. Furthermore, repositioning of nucleosomes occurred rapidly after glucose repression. Because nucleosomal disruption and transcription produce topological changes in the chromatin substrate, the effect of topoisomerase activity was tested by the insertion of GAL-URABIB in topoisomerase mutant strains. The chromatin structure was analysed by nuclease digestion and psoralen crosslinking, and compared with that of the rDNA locus. In GAL-URARIB, neither the inactivation of topoisomerases I, II or I and II generated nucleosomal loss during transcription, nor was topoisomerase activity required for repositioning of the nucleosomes after repression. In contrast, the inactivation of topoisomerase I promoted an enhanced psoralen accessibility of the transcribed rDNA, possibly because of altered supercoiling, and the inactivation of topoisomerases I and II disrupted the chromatin structure of the whole rDNA locus by redistribution of the nucleosomes. The inactivation of topoisomerase II alone had no effect. These observations substantiate a differential participation of topoisomerases in the modulation of the chromatin structures of rDNA genes and of a single copy polymerase II gene. It is suggested that topological stress in genes transcribed by RNA polymerase II might diffuse away into flanking regions.
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PMID:Inactivation of topoisomerases affects transcription-dependent chromatin transitions in rDNA but not in a gene transcribed by RNA polymerase II. 859 42

To investigate the importance of topoisomerases for transcription of the galactose induced genes, we have studied the expression of GAL1, GAL2, GAL7 and GAL10 in Saccharomyces cerevisiae cells deficient for topoisomerases I and II. We find that topoisomerases are required for transcriptional activation of the GAL genes, but are dispensable for ongoing transcription, eliminating a role of the enzymes in transcriptional elongation. Furthermore, we demonstrate that promoter chromatin remodeling of the GAL genes is unaffected in the topoisomerase deficient strain. However, the cells fail to successfully recruit RNA polymerase II due to an inability of the TATA-binding protein (TBP) to bind to the TATA box in these promoters. We therefore argue that topoisomerases are required for accurate assembly of the preinitiation complex at the promoters of the GAL genes.
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PMID:DNA Topoisomerases Are Required for Preinitiation Complex Assembly during GAL Gene Activation. 2617 27