Jj. Stewart et La. Stargell, The stability of the TFIIA-TBP-DNA complex is dependent on the sequence ofthe TATAAA element, J BIOL CHEM, 276(32), 2001, pp. 30078-30084
To determine the mechanistic differences between canonical and noncanonical
TATA elements, we compared the functional activity of two sequences: TATAA
A (canonical) and CATAAA (noncanonical). The TATAAA element can support hig
h levels of transcription in vivo, whereas the CATAAA element is severely d
efective for this function.. This dramatic functional difference is not lik
ely to be due to a difference in TBP (TATA-binding protein) binding efficie
ncy because protein-DNA complex studies in vitro indicate little difference
between the two DNA sequences in the formation and stability of the TBP-DN
A complex. In addition, the binding and stability of the TFIIB-TBP-DNA comp
lex is similar for the two elements. In striking contrast, the TFIIA-TBP-DN
A complex is significantly less stable on the CATAAA element when compared
with the TATAAA element. A role for TFIIA in distinguishing between TATAAA
and CATAAA in vivo was tested by fusing. a subunit of TFIIA to TBP. We foun
d that fusion of TFIIA to TBP dramatically increases transcription from CAT
AAA, in yeast cells. Taken together, these results indicate that the stabil
ity of the TFIIA-TBP complex depends strongly on the sequence of the core p
romoter element and that the TFIIA-TBP complex plays an important function
in recognizing optimal promoters in vivo.