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Formation of a Monomeric DNA Binding Domain by Skn-1 bZIP and Homeodomain Elements

T. Keith Blackwell, Bruce Bowerman, James R. Priess and Harold Weintraub
Science
New Series, Vol. 266, No. 5185 (Oct. 28, 1994), pp. 621-628
Stable URL: http://www.jstor.org/stable/2885441
Page Count: 8
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Formation of a Monomeric DNA Binding Domain by Skn-1 bZIP and Homeodomain Elements
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Abstract

Maternally expressed Skn-1 protein is required for the correct specification of certain blastomere fates in early Caenorhabditis elegans embryos. Skn-1 contains a basic region similar to those of basic leucine zipper (bZIP) proteins but, paradoxically, it lacks a leucine zipper dimerization segment. Random sequence selection methods were used to show that Skn-1 binds to specific DNA sequences as a monomer. The Skn-1 basic region lies at the carboxyl terminus of an 85-amino acid domain that binds preferentially to a bZIP half-site and also recognizes adjacent 5' AT-rich sequences in the minor groove, apparently with an amino (NH$_2$)-terminal "arm" related to those of homeodomain proteins. The intervening residues appear to stabilize interactions of these two subdomains with DNA. The Skn-1 DNA binding domain thus represents an alternative strategy for promoting binding of a basic region segment recognition helix to its cognate half-site. The results point to an underlying modularity in subdomains within established DNA binding domains.

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