Murine p53 inhibits the function but not the formation of SV40 T antigen hexamers and stimulates T antigen RNA helicase activity.
We have characterized the effects of p53 on several biochemical activities of simian virus 40 (SV40) large tumor (T) antigen. While p53 induced a strong inhibition of the T antigen DNA helicase activity, surprisingly, its RNA helicase activity was stimulated. This supports the liklihood that the DNA and RNA helicase activities of T antigen reflect discrete functions. p53 did not significantly affect the ATP-dependent conversion of T antigen monomers to hexamers. However, the ability of these hexamers to assemble on a DNA fragment containing the viral origin was impaired by p53. Thus, these results suggest that p53 inhibits the function but not the formation of T antigen multimers. This conclusion was further supported by the observation that the addition of a purified p53:T antigen complex was as inhibitory as free p53 to the DNA helicase activity of free T antigen. Thus our data indicates that the targets of p53 inhibition are the functional units of T antigen, namely the hexamers.
Friedman
P N
PN
Department of Biological Sciences, Columbia University, New York, NY 10027.
Wang
E H
EH
Meerovitch
K
K
Sonenberg
N
N
Prives
C
C
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D004265:DNA Helicases / Q000037:antagonists & inhibitors*; D004261:DNA Replication / Q000502:physiology*; D051379:Mice; D009036:Moths; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000037:antagonists & inhibitors*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D000952:Antigens, Polyomavirus Transforming; D016159:Tumor Suppressor Protein p53; D012316:RNA Nucleotidyltransferases; D004265:DNA Helicases; D020365:RNA Helicases