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SoSSB_OBF: A subfamily of OB folds similar to the OB fold of the crenarchaeote Sulfolobus solfataricus single-stranded (ss) DNA-binding protein (SSoSSB). SSoSSB has a single OB fold, and it physically and functionally interacts with RNA polymerase. In vitro, SSoSSB can substitute for the basal transcription factor TBP, stimulating transcription from promoters under conditions in which TBP is limiting, and supporting transcription when TBP is absent. SSoSSB selectively melts the duplex DNA of promoter sequences. It also relieves transcriptional repression by the chromatin Alba. In addition, SSoSSB activates reverse gyrase activity, which involves DNA binding, DNA cleavage, strand passage and ligation. SSoSSB stimulates all these steps in the presence of the chromatin protein, Sul7d. SSoSSB antagonizes the inhibitory effect of Sul7d on reverse gyrase supercoiling activity. It also physically and functionally interacts with Mini-chromosome Maintenance (MCM), stimulating the DNA helicase activity of MCM.
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