title: Characterization of chicken octamer-binding proteins demonstrates that POU domain-containing homeobox transcription factors have been highly conserved during vertebrate evolution.
abstract: The DNA sequence motif ATTTGCAT (octamer) or its inverse complement has been identified as an evolutionarily conserved element in the promoter region of immunoglobulin genes. Two major DNA-binding proteins that bind in a sequence-specific manner to the octamer DNA sequence have been identified in mammalian species--a ubiquitously expressed protein (Oct-1) and a lymphoid-specific protein (Oct-2). During characterization of the promoter region of the chicken immunoglobulin light chain gene, we identified two homologous octamer-binding proteins in chicken B cells. When the cloning of the human gene for Oct-2 revealed it to be a member of a distinct family of homeobox genes, we sought to determine if the human Oct-2 cDNA could be used to identify homologous chicken homeobox genes. Using a human Oct-2 homeobox-specific DNA probe, we were able to identify 6-10 homeobox-containing genes in the chicken genome, demonstrating that the Oct-2-related subfamily of homeobox genes exists in avian species. Low-stringency screening of a chicken embryonic cDNA library allowed us to clone one of these genes. DNA sequence analysis revealed it to be the chicken homologue of the human Oct-1 gene. The predicted protein sequence of the chicken Oct-1 gene demonstrated that the gene for Oct-1 has been highly conserved during vertebrate evolution with an overall 96% amino acid sequence identity between the chicken and human proteins. The previously described POU domain (termed POU for its presence in the Pit-1, Oct-1/Oct-2, and Unc-86 genes) and homeobox domain are 100% conserved between the two protein products. Together, our data show that the POU-containing subfamily of homeobox genes have been highly conserved during vertebrate evolution, apparently as a result of selection for their DNA-binding and transcriptional regulatory properties.
authors.affiliation: Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109.
authors.forename: B
authors.initials: B
authors.lastname: Petryniak
authors.forename: L M
authors.initials: LM
authors.lastname: Staudt
authors.forename: C E
authors.initials: CE
authors.lastname: Postema
authors.forename: W T
authors.initials: WT
authors.lastname: McCormack
authors.forename: C B
authors.initials: CB
authors.lastname: Thompson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis; D002645:Chickens / Q000235:genetics*; D004247:DNA / Q000235:genetics; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000235:genetics*; D005796:Genes; D005801:Genes, Homeobox; D005803:Genes, Immunoglobulin; D051863:Host Cell Factor C1; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000235:genetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014714:Vertebrates / Q000235:genetics*
chemical_list: D015342:DNA Probes; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D007147:Immunoglobulin Light Chains; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D014157:Transcription Factors; D004247:DNA