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Mol. Cell. Biol., Jan 1998, 361-367, Vol 18, No. 1
R Sandaltzopoulos and PB Becker
Transcription by RNA polymerase II is highly regulated at the level of
initiation and elongation. Well-documented transcription activation
mechanisms, such as the recruitment of TFIID and TFIIB, control the early
phases of preinitiation complex formation. The heat shock genes provide an
example for transcriptional regulation at a later step: in nuclei TFIID can
be detected at the TATA box prior to heat induction. Using cell-free
systems for chromatin reconstitution and transcription, we have analyzed
the mechanisms by which heat shock factor (HSF) increases transcription of
heat shock genes in chromatin. HSF affected transcription of naked DNA
templates in multiple ways: (i) by speeding up the rate of preinitiation
complex formation, (ii) by increasing the number of productive templates,
and (iii) by increasing the reinitiation rate. Under the more physiological
conditions of potentiated chromatin templates, HSF affected only the
reinitiation rate. Activator-dependent reinitiation of transcription,
obviating the slow assembly of the TFIID-TFIIA complex on a promoter, may
be especially crucial for genes requiring a fast response to inducers.
Copyright © 1998, American Society for Microbiology
Heat shock factor increases the reinitiation rate from potentiated chromatin templates
Gene Expression Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
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