The human DNA-activated protein kinase phosphorylates simian virus 40 T antigen at amino- and carboxy-terminal sites.
Protein phosphorylation modulates the functions of simian virus 40 large T antigen (TAg) in productive and transforming infections. We recently described a DNA-activated protein kinase (DNA-PK) that efficiently phosphorylates TAg and several other nuclear, DNA-binding proteins in vitro (S.P. Lees-Miller, Y.-R. Chen, and C. W. Anderson, Mol. Cell. Biol. 10:6472-6481, 1990). In this report, we show by direct amino acid sequence analysis that DNA-PK phosphorylates TAg strongly at Ser-677, a residue known to be important for TAg interaction with origin site I and for transformation. We propose that DNA-PK may modulate the role of TAg in repressing early viral transcription and cell transformation, but a role for DNA-PK in regulating simian virus 40 DNA synthesis is not excluded. DNA-PK also phosphorylates Ser-665, and Ser-667, and one or more serines between amino acids 110 and 131. At least six serines, Ser-111, Ser-112, Ser-120, Ser-665, Ser-667, and Ser-677, are phosphorylated in TAg purified from baculovirus vector-infected insect cells.
Chen
Y R
YR
Biology Department, Brookhaven National Laboratory, Upton, New York 11973.
Lees-Miller
S P
SP
Tegtmeyer
P
P
Anderson
C W
CW
D000595:Amino Acid Sequence; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016367:Baculoviridae / Q000235:genetics; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism*; D005822:Genetic Vectors; D006801:Humans; D007313:Insecta; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D010710:Phosphates / Q000378:metabolism; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013539:Simian virus 40 / Q000276:immunology* / Q000378:metabolism
D000952:Antigens, Polyomavirus Transforming; D010446:Peptide Fragments; D010710:Phosphates; D010748:Phosphopeptides; D011994:Recombinant Proteins; D004247:DNA; D011494:Protein Kinases