Rich Friedman writes:
>I am wondering if anyone has heard of a transcription factor which has two
>activation sites. I am trying to find out if a factor which binds to an
>enhancer sequence, has the ability to stimulate expression from two promoters,
>simultaneously. I think that this would require that the factor would have to
>have two activation sites. If you any info, please e-mail me .
There are some transcription factors (TFs) that have multiple DNA
binding domains - Mike Levine's lab characterized one (the name escapes me
at the moment but I could look it up) that had both a "paired" box and a
homeobox (homoeobox for the Brits) and both could bind to completely
different (although in their original work, overlapping) sites. Recently,
TFs have been cloned which have large numbers of Zn fingers (>15), many of
which seem to be capable of binding DNA, and also recently someone cloned a
monster that had multiple homeoboxes AND multiple Zn fingers.
If your question is whether a TF with only one DNA binding site can
activate multiple genes, then the answer is also yes, with examples too
numerous to cover. A favorite example is the anterior pituitary-specific
Pit1 (aka (if inaccurately) as GHF1) which can activate transcription from
both the Prolactin promoter (and in fact is absolutely required for PRL
expression), Growth Hormone promoter (less tightly regulated than PRL), and
TSH gene, as well as its own promoter (all anterior pituitary-specific
genes).
Hope this is of some help
Cheers,
Harry
Harry Mangalam Vox:(619) 453-4100, x250
Dept of Biocomputing Fax:(619) 552-1546
The Salk Institute 1' mangalam at salk-sc2.sdsc.edu
10010 N Torrey Pines Rd 2' hjm at salk-sgi.sdsc.edu
La Jolla CA 92037 3' mangalam at salk.bitnet
