The p53 complex from monkey cells modulates the biochemical activities of simian virus 40 large T antigen.
We have compared the ATPase, DNA-binding, and helicase activities of free simian virus 40 (SV40) large T antigen (To) and T antigen complexed with cellular p53 (T+p53). Each activity is essential for productive viral infection. The T+p53 and To fractions were prepared by sequential immunosorption of infected monkey cells with monoclonal antibodies specific for p53 and T antigen. The immune-complexed T fractions were then assayed in parallel. For ATP hydrolysis, the Vmax for T+p53 was 143 nmol of ADP per min per mg of protein, or 18-fold greater than for To. ATP had no effect on the stability of the T+p53 complex. The T+p53 complex was significantly more active than To in hydrolyzing dATP, dGTP, GTP, and UTP. Of the nucleotide substrates tested, the greatest relative increase (T+p53/To) was in hydrolyzing dGTP and GTP. In DNase footprinting assays performed under replication conditions, the T+p53 complex protected regions I, II, and III of origin DNA while equivalent amounts of To protected only regions I and II. Region III is known to contribute to the efficiency of DNA replication and contains the SP1-binding sites of the early viral promoter. The T+p53 fraction was also a more efficient helicase than To, especially with a GC-rich primer and template. Thus, the T+p53 complex has enhanced ATPase, GTPase, DNA-binding, and helicase activities. These findings imply that complex formation between cellular monkey p53 and SV40 T antigen modulates a number of essential activities of T in SV40 productive infection.
Tack
L C
LC
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92138.
Wright
J H
JH
Deb
S P
SP
Tegtmeyer
P
P
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000952:Antigens, Polyomavirus Transforming / Q000502:physiology*; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000502:physiology; D004338:Drug Combinations; D020558:GTP Phosphohydrolases / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D009363:Neoplasm Proteins / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D011485:Protein Binding / Q000187:drug effects; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D016159:Tumor Suppressor Protein p53
D000952:Antigens, Polyomavirus Transforming; D004268:DNA-Binding Proteins; D004338:Drug Combinations; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D016159:Tumor Suppressor Protein p53; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D020558:GTP Phosphohydrolases; D004265:DNA Helicases