SIMIAN-VIRUS-40 LARGE T-ANTIGEN INTERACTS WITH HUMAN TFIIB-RELATED FACTOR AND SMALL NUCLEAR RNA-ACTIVATING PROTEIN COMPLEX FOR TRANSCRIPTIONAL ACTIVATION OF TATA-CONTAINING POLYMERASE-III PROMOTERS
B. Damania et al., SIMIAN-VIRUS-40 LARGE T-ANTIGEN INTERACTS WITH HUMAN TFIIB-RELATED FACTOR AND SMALL NUCLEAR RNA-ACTIVATING PROTEIN COMPLEX FOR TRANSCRIPTIONAL ACTIVATION OF TATA-CONTAINING POLYMERASE-III PROMOTERS, Molecular and cellular biology, 18(3), 1998, pp. 1331-1338
The TATA-binding protein (TBP) is common to the basal transcription fa
ctors of all three RNA polymerases, being associated with polymerase-s
pecific TBP-associated factors (TAFs). Simian virus 40 large T antigen
has previously been shown to interact with the TBP-TAFII complexes, T
FIID (B. Damania and J. C. Alwine, Genes Dev. 10:1369-1381, 1996), and
the TBP-TAF(I) complex, SL1 (W. Zhai, J. Tuan, and L. Comai, Genes De
v. 11: 1605-1617, 1997), and in both cases these interactions are crit
ical for transcriptional activation, We show a similar mechanism for a
ctivation of the class 3 polymerase III (pol III) promoter for the U6
RNA gene. Large T antigen can activate this promoter, which contains a
TATA box and an upstream proximal sequence element but cannot activat
e the TATA-less, intragenic VAI promoter (a class 2, pol III promoter)
, Mutants of large T antigen that cannot activate pol II promoters als
o fail to activate the U6 promoter, We provide evidence that large T a
ntigen can interact with the TBP-containing pol III transcription fact
or human TFIIB-related factor (hBRF), as well as with at least two of
the three TAFs in the pol III-specific small nuclear RNA-activating pr
otein complex (SNAPc), In addition, we demonstrate that large T antige
n can cofractionate and coimmunoprecipitate with the hBRF-containing c
omplex TFIIIB derived from HeLa cells infected with a recombinant aden
ovirus which expresses large T antigen, Hence, similar to its function
with pol I and pol II promoters, large T antigen interacts with TBP-c
ontaining, basal pol III transcription factors and appears to perform
a TAF-like function.