Formation of a monomeric DNA binding domain by Skn-1 bZIP and homeodomain elements.
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 (NH2)-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.
Blackwell
T K
TK
Department of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
Bowerman
B
B
Priess
J R
JR
Weintraub
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D051790:G-Box Binding Factors; D015801:Helminth Proteins / Q000737:chemistry / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors
D050976:Basic-Leucine Zipper Transcription Factors; D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D015801:Helminth Proteins; D018398:Homeodomain Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C073702:skn-1 protein, C elegans; D004247:DNA