Recognition of the surface of a homeo domain protein.
Homeo domain proteins exhibit distinct biological functions with specificities that cannot be predicted by their sequence specificities for binding DNA. Recognition of the surface of the Oct-1 POU homeo domain provides a general model for the contribution of selective protein-protein interactions to the functional specificity of the homeo domain family of factors. The assembly of Oct-1 into a multiprotein complex on the herpes simplex virus alpha/IE enhancer is specified by the interactions of its homeo domain with ancillary factors. This complex (C1 complex) is composed of the viral alpha TIF protein (VP16), Oct-1, and one additional cellular component, the C1 factor. Variants of the Oct-1 POU homeo domain were generated by site-directed mutagenesis, which altered the residues predicted to form the exposed surface of the domain-DNA complex. Proteins with single amino acid substitutions on the surface of either helix 1 or 2 of the Oct-1 POU homeo domain had decreased abilities to form the C1 complex. The behavior of these mutants in a cooperative DNA-binding assay with alpha TIF suggested that the Oct-1 POU homeo domain is principally recognized by alpha TIF in the C1 complex. The preferential recognition of Oct-1 over the closely related Oct-2 protein is critically influenced by a single residue on the surface of helix 1 because the introduction of this residue into the Oct-2 POU homeo domain significantly enhanced its ability to form a C1 complex.
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
J L
JL
Pomerantz
T M
TM
Kristie
P A
PA
Sharp
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005801:Genes, Homeobox; D051863:Host Cell Factor C1; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013211:Staphylococcus aureus / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D015342:DNA Probes; D004268:DNA-Binding Proteins; D051863:Host Cell Factor C1; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D009838:Oligodeoxyribonucleotides; C058435:POU2F2 protein, human; D014157:Transcription Factors