RNA helicase activity associated with the human p68 protein.
It has been proposed that p68, a nuclear protein of relative molecular mass 68,000, functions in the regulation of cell growth and division. A complementary DNA analysis of the protein has revealed extensive amino-acid sequence homology to the products of a set of genes recently identified in organisms as diverse as Escherichia coli and man, which include the eukaryotic translation initiation factor elF-4A. The protein products of the new gene family have several motifs in common which are thought to be involved in nucleic acid unwinding. As yet, however, only elF-4A, through its effect on RNA, has been shown to possess unwinding activity. Here we report that purified p68 also exhibits RNA-dependent ATPase activity and functions as an RNA helicase in vitro. The protein was first identified by its specific immunological cross reaction with the simian virus 40 large T antigen, the transforming protein of a small DNA tumour virus. Surprisingly, T antigen also has an RNA-unwinding activity: the homology between the two polypeptides, although confined to only a small region resembling the epitope of the cross-reacting antibody (PAb204), should therefore be of functional significance. Furthermore, the RNA-unwinding activity may be involved in the growth-regulating functions of both proteins.
Hirling
H
H
Fakultät für Biologie, Universität Konstanz, FRG.
Scheffner
M
M
Restle
T
T
Stahl
H
H
D000251:Adenosine Triphosphatases / Q000378:metabolism; D053487:DEAD-box RNA Helicases; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D066298:In Vitro Techniques; D009687:Nuclear Proteins / Q000502:physiology*; D011494:Protein Kinases; D012313:RNA / Q000378:metabolism*; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*
D009687:Nuclear Proteins; D012313:RNA; D011494:Protein Kinases; D012316:RNA Nucleotidyltransferases; D000251:Adenosine Triphosphatases; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases