An altered-specificity mutation in a human POU domain demonstrates functional analogy between the POU-specific subdomain and phage lambda repressor.
The POU motif, conserved among a family of eukaryotic transcription factors, contains two DNA-binding domains: an N-terminal POU-specific domain (POUS) and a C-terminal homeodomain (POUHD). Surprisingly, POUS is similar in structure to the helix-turn-helix domains of bacteriophage repressor and Cro proteins. Such similarity predicts a common mechanism of DNA recognition. To test this prediction, we have studied the DNA-binding properties of the human Oct-2 POU domain by combined application of chemical synthesis and site-directed mutagenesis. The POUS footprint of DNA contacts, identified by use of modified bases, is analogous to those of bacteriophage repressor-operator complexes. Moreover, a loss-of-contact substitution in the putative POUS recognition alpha-helix leads to relaxed specificity at one position in the DNA target site. The implied side chain-base contact is identical to that of bacteriophage repressor and Cro proteins. These results establish a functional analogy between the POUS and prokaryotic helix-turn-helix elements and suggest that their DNA specificities may be governed by a shared set of rules.
Jancso
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A
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Botfield
M C
MC
Sowers
L C
LC
Weiss
M A
MA
D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry*; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050813:Octamer Transcription Factor-2; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; D050813:Octamer Transcription Factor-2; C058435:POU2F2 protein, human; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins