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Human p53, a 53 Kd protein, is composed of 393 amino acids. As
a transcriptional factor, it plays a major role in cellular
growth , differentiation and DNA repair. It has been found that
p53 protein can form complex with a number of viral
transforming antigens, such as large T antigen of SV40, E1B
antigen of adenovirus. It is thought that the inhibition of
normal p53 function may be an essential step in cellular
trnsformation.It was previously established that formation of
the complex of viral transforming antigen with p53 could
interfere with its DNA binding ability and thus its
transcriptional activity. In this way, p53 protein was rendered
functionless. Despite this, we discovered that the p53-large T
complex still retained DNA binding ability in COS-1, a large T
transformed African monkey cell line, and in 1A3, a temperature-
sensitive SV40-transformed murine pituitary cell line. By using
gel retardation assay, we found that the p53 could bind
specifically to RGC and consensus probe. Addition of anti-p53
and large T antibodies can produce supershifting of the bands.
In addition, the combined gel retardation immunoblot experiment
showed that the large T antigen and p53 exited in the same
band. Our results suggest that the large T antigen-p53 complex
can bind to DNA. It can be deduced that large T antigen
interfere with p53 functioning either by directly inhibiting
binding of p53 to its cognate site or by indirectly repressing
the transcriptional activity of DNA- bound p53.
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