Mike S. Fenton and Jay D. Gralla*
Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Post Office Box 951569, Los Angeles, CA 90095-1569
* To whom reprint requests should be addressed. E-mail:
gralla@chem.ucla.edu
The bacterial TATAAT -10 region sequence was the first promoter element
to be identified, but how it functions is still not clear. Because
the duplex element is melted during initiation, the effects
of substitutions were studied in both single-and double-strand contexts.
Band-shift results were particularly unexpected in the context
of melted DNA. The effect of the lac UV5-melted -10 region on
polymerase binding was found to include a large sequence nonspecific contribution.
Instead the dominant role of single-stranded -10region nucleotides was
in directing the isomerization of the RNA polymerase to its heparin resistant
form. This role becomes minimal when the melting is extended beyond the
-10 region to encompass the transcription start site, as in the final open
complex. The duplex binding results are in agreement with previous reports
that showed positions -12T and -11A are of primary importance for promoter
recognition. Thus the consensus -10 region sequences function in two ways,
both before full promoter melting. They stabilize initial polymerase binding
via duplex interactions and subsequently as single-stranded DNA they promote
enzyme isomerization to the functional form.
1. "Selective Control of DNA Helix Openings During Gene Regulation".
2. "Activation of DNA Transcription within Repressed Chromatin by Nuclear RNA Species".
Top of Page - Euchromatin Network - Current Research - Forums - Other Sites - Future Events -