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Mol. Cell. Biol., May 1996, 2135-2143, Vol 16, No. 5
J Mead, H Zhong, TB Acton and AK Vershon
Homeodomain proteins are transcriptional regulatory factors that, in
general, bind DNA with relatively low sequence specificity and affinity.
One mechanism homeodomain proteins use to increase their biological
specificity is through interactions with other DNA-binding proteins. We
have examined how the yeast (Saccharomyces cerevisiae) homeodomain protein
alpha2 specifically interacts with Mcm1, a MADS box protein, to bind DNA
specifically and repress transcription. A patch of predominantly
hydrophobic residues within a region preceding the homeodomain of alpha2
has been identified that specifies direct interaction with Mcm1 in the
absence of DNA. This hydrophobic patch is required for cooperative DNA
binding with Mcm1 in vitro and for transcriptional repression in vivo. We
have also found that a conserved motif, termed YPWM, frequently found in
homeodomain proteins of insects and mammals, partially functions in place
of the patch in alpha2 to interact with Mcm1. These findings suggest that
homeodomain proteins from diverse organisms may use analogous interaction
motifs to associate with other proteins to achieve high levels of DNA
binding affinity and specificity.
Copyright © 1996, American Society for Microbiology
The yeast alpha2 and Mcm1 proteins interact through a region similar to a motif found in homeodomain proteins of higher eukaryotes
Waksman Institute, Rutgers University, Piscataway, New Jersey 08855- 0759, USA.
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