B. Damania et al., SIMIAN-VIRUS-40 LARGE T-ANTIGEN STABILIZES THE TATA-BINDING PROTEIN TFIIA COMPLEX ON THE TATA ELEMENT, Molecular and cellular biology, 18(7), 1998, pp. 3926-3935
Large T antigen (T antigen), the early gene product of simian virus 40
(SV40), is a potent transcriptional activator of both cellular and vi
ral genes. Recently we have shown that T antigen is tightly associated
with TFIID and, in this position, performs a TATA-binding protein (TB
P)-associated factor (TAF)-like function. Based on this observation, w
e asked whether T antigen affected steps in preinitiation complex asse
mbly. Using purified components in in vitro complex assembly assays, w
e found that T antigen specifically enhances the formation of the TBP-
TFIIA complex on the TATA element. T antigen accomplishes this by incr
easing the rate of formation of the TBP-TFIIA complex on the TATA elem
ent and by stabilizing the complexes after they are formed on the prom
oter. In addition, DNA immunoprecipitation experiments indicate that T
antigen is associated with the stabilized TBP-TFIIA complexes bound t
o the DNA. In this regard, it has previously been shown that T antigen
interacts with TBP; in the present study, we show that T antigen also
interacts with TFIIA in vitro. In testing the ability of T antigen to
stabilize the TBP-TFIIA complex, we found that stabilization is highl
y sensitive to the specific sequence context of the TATA element. Prev
ious studies showed that T antigen could activate simple promoters con
taining the TATA elements from the hsp70 and c-fos gene promoters but
failed to significantly activate similar promoters containing the TATA
elements from the promoters of the SV40 early and adenovirus E2a gene
s. We find that the ability to stabilize the TBP-TFIIIA complex on the
hsp70 and c-fos TATA elements, and not on the SV40 early and E2A TATA
elements, correlates with the ability or inability to activate promot
ers containing these TATA elements.