Article Abstract:
A positive transcription elongation factor b (P-TEFb) may control transition from abortive to productive elongation through phosphorylation of the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II. Drosophila P-TEFb has been shown to be a cyclin-dependent kinase (CDK9). Cloning of multiple cyclin subunits of human P-TEFb (T1 and T2) has been carried out. Cyclin T1 and T2 are expressed ubiquitously. Immunoprecipitation and immunodepletion experiments have indicated that cyclin T1 and T2 were associated in a mutually exclusive way with CDK9, almost all of which was associated with one or the other.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
In eukaryotes and in prokaryotes it appears that transcription can be activated by arbitrary contacts between DNA-bound proteins and components of transcriptional mechanisms. The Escherichia coli omega protein, which copurifies with RNA polymerase, can act as a transcriptional activator when covalent linkage to a DNA-binding protein occurs. It seems that the omega protein and RNA polymerase holoenzyme are associated in vivo. Evidence indicates that transcription can be activated by contact between a DNA-bound protein and any subunit of E. coli RNA polymerase.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
The bacteriophage lambda repressor and P22 repressors have been studied. Protein-protein interaction between DNA-bound dimers mediates cooperativity in which the repressors bind to adjacent and artificially separated operator sites. A genetic approach has been used to identify pairs of amino acids that interact at the dimer-dimer interface. Individual substitutions stop the interaction of the DNA-bound dimers, but changes in combination bring back interaction of lambda cI and P22c2 dimers.
User Contributions:
Comment about this article or add new information about this topic: