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Figure 4.
Fig. 4. Simplified model for assembly of transcription
complexes on chromatin-bound templates. First, recruitment of a
HAT-containing coactivator complex via interactions with an
upstream DNA binding protein occurs. After recruitment, the
coactivator HAT activity might acetylate the NH[2]-terminal
histone tails (light blue tails) of nearby nucleosomes (upper).
Acetylated histone tails positioned at an appropriate distance
from the start site of a gene might then help to recruit TFIID
by interactions with the TAF[II]250 bromodomains. Nonspecific
interactions between the TAF[II]250 bromodomains and the
promoter DNA as well as other TAF-DNA interactions could further
increase affinity of TFIID for the core promoter. The
bromodomain-mediated increase in affinity for the acetylated
histones near the core promoter would provide a linkage between
histone acetylation and transcriptional activation by enhanced
preinitiation complex formation. Such a model would not preclude
other activation pathways.
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