Ku autoantigen is the regulatory component of a template-associated protein kinase that phosphorylates RNA polymerase II.
The carboxyl-terminal domain of RNA polymerase II contains a tandemly repeated heptapeptide sequence. Previous work has shown that this sequence is phosphorylated at multiple sites by a template-associated protein kinase, in a reaction that is closely associated with the initiation of RNA synthesis. We have purified this kinase to apparent homogeneity from human (HeLa) cells. The purified kinase phosphorylates native RNA polymerase II only in the presence of DNA and the general transcription factors TFIID (TBP), TFIIB, and TFIIF. Two kinase components are required for full activity: a catalytic component and a DNA-binding regulatory component. The regulatory component has been identified as Ku autoantigen, based on the molecular weights of its component polypeptides, its DNA-binding properties, and its reactivity with anti-Ku monoclonal antibodies. The Ku autoantigen recruits the catalytic component of the kinase to the template. Ku autoantigen has been previously proposed to interact with DNA by a characteristic bind-and-slide mechanism. This mode of interaction may provide a mechanism for targeting the kinase to the transcription complex and other DNA-bound substrates.
Dvir
A
A
Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
Peterson
S R
SR
Knuth
M W
MW
Lu
H
H
Dynan
W S
WS
D034961:Antigens, Nuclear; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D013698:Templates, Genetic
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011494:Protein Kinases; D012319:RNA Polymerase II; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen