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Mol. Cell. Biol., Jul 1997, 3799-3808, Vol 17, No. 7
JA Weber, DJ Taxman, Q Lu and DS Gilmour
GAGA factor, TFIID, and paused polymerase are present on the hsp70 promoter
in Drosophila melanogaster prior to transcriptional activation. In order to
investigate the interplay between these components, mutant constructs were
analyzed after they had been transformed into flies on P elements. One
construct lacked the TATA box and the other lacked the upstream regulatory
region where GAGA factor binds. Transcription of each mutant during heat
shock was at least 50- fold less than that of a normal promoter construct.
Before and after heat shock, both mutant promoters were found to adopt a
DNase I hypersensitive state that included the region downstream from the
transcription start site. High-resolution analysis of the DNase I cutting
pattern identified proteins that could be contributing to the
hypersensitivity. GAGA factor footprints were clearly evident in the
upstream region of the TATA deletion construct, and a partial footprint
possibly caused by TFIID was evident on the TATA box of the upstream
deletion construct. Permanganate treatment of intact salivary glands was
used to further characterize each promoter construct. Paused polymerase and
TFIID were readily detected on the normal promoter construct, whereas both
deletions exhibited reduced levels of each of these factors. Hence both the
TATA box and the upstream region are required to efficiently recruit TFIID
and a paused polymerase to the promoter prior to transcriptional
activation. In contrast, GAGA factor appears to be capable of binding and
establishing a DNase I hypersensitive region in the absence of TFIID and
polymerase. Interestingly, purified GAGA factor was found to bind near the
transcription start site, and the strength of this interaction was
increased by the presence of the upstream region. GAGA factor alone might
be capable of establishing an open chromatin structure that encompasses the
upstream regulatory region as well as the core promoter region, thus
facilitating the binding of TFIID.
Copyright © 1997, American Society for Microbiology
Molecular architecture of the hsp70 promoter after deletion of the TATA box or the upstream regulation region
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA.
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