Al. Roy et al., CLONING OF AN INR-BINDING AND E-BOX-BINDING PROTEIN, TFII-I, THAT INTERACTS PHYSICALLY AND FUNCTIONALLY WITH USF1, EMBO journal, 16(23), 1997, pp. 7091-7104
The transcription factor TFII-I has been shown to bind independently t
o two distinct promoter elements, a pyrimidine-rich initiator (Inr) an
d a recognition site (E-box) for upstream stimulatory factor 1 (USF1),
and to stimulate USF1 binding to both of these sites. Here we describ
e the isolation of a cDNA encoding TFII-I and demonstrate that the cor
responding 120 kDa polypeptide, when expressed ectopically, is capable
of binding to both Inr and E-box elements. The primary structure of T
FII-I reveals novel features that include six directly repeated 90 res
idue motifs that each possess a potential helix-loop/span-helix homolo
gy, These unique structural features suggest that TFII-I may have the
capacity for multiple protein-protein and, potentially, multiple prote
in-DNA interactions, Consistent with this hypothesis and with previous
in vitro studies, we further demonstrate that ectopic TFII-I and USF1
can act synergistically, and in some cases independently, to activate
transcription in vivo through both Inr and the E-box elements of the
adenovirus major late promoter, We also describe domains of USF1 that
are necessary for its independent and synergistic activation functions
.