POU proteins are eukaryotic transcription factors containing a bipartite DNA binding domain referred to as the POU domain. The acronym POU (pronounced 'pow') is derived from the names of three mammalian transcription factors, the pituitary-specific Pit-1, the octamer-binding proteins Oct-1 and Oct-2, and the neural Unc-86 from Caenorhabditis elegans. POU domain genes have been identified in diverse organisms including nematodes, flies, amphibians, fish and mammals but have not been yet identified in plants and fungi. The various members of the POU family have a wide variety of functions, all of which are related to the function of the neuroendocrine system [ (PUBMED:8462099) ] and the development of an organism [ (PUBMED:11159814) ]. Some other genes are also regulated, including those for immunoglobulin light and heavy chains (Oct-2) [ (PUBMED:1967834) (PUBMED:1967821) ], and trophic hormone genes, such as those for prolactin and growth hormone (Pit-1).
The POU domain is a bipartite domain composed of two subunits separated by a non-conserved region of 15-55 aa. The N-terminal subunit is known as the POU-specific (POUs) domain ( IPR000327 ), while the C-terminal subunit is a homeobox domain ( IPR001356 ). 3D structures of complexes including both POU subdomains bound to DNA are available. Both subdomains contain the structural motif 'helix-turn-helix', which directly associates with the two components of bipartite DNA binding sites, and both are required for high affinity sequence-specific DNA-binding. The domain may also be involved in protein-protein interactions [ (PUBMED:1628619) ]. The subdomains are connected by a flexible linker [ (PUBMED:11183772) (PUBMED:8156594) (PUBMED:9009203) ]. In proteins a POU-specific domain is always accompanied by a homeodomain. Despite of the lack of sequence homology, 3D structure of POUs is similar to 3D structure of bacteriophage lambda repressor and other members of HTH_3 family [ (PUBMED:11183772) (PUBMED:8156594) ].
This entry represents the POU-specific subunit of the POU domain.
GO process:
regulation of transcription, DNA-templated (GO:0006355)
The solution structure of the Oct-1 POU-specific domain reveals a striking similarity to the bacteriophage lambda repressor DNA-binding domain.
Cell. 1993; 73: 193-205
Display abstract
The POU-specific (POUs) domain, in association with a POU-type homeodomain, forms the bipartite DNA-binding POU domain. The solution structure of the Oct-1 POUs domain has been determined by multidimensional nuclear magnetic resonance spectroscopy and consists of four alpha helices surrounding a conserved hydrophobic core. The POUs domain is structurally similar to the DNA-binding domains of the bacteriophage lambda and 434 repressors and 434 Cro. These domains exhibit superimposable helix-turn-helix (HTH) motifs, except that in the POUs domain, the first helix and the linker to the second helix of the motif are extended. The conserved structural features have been used to propose a plausible model for DNA binding by the POUs domain. A human dwarfism mutation that affects positive control in the related POU domain protein Pit-1 maps to the same region of the HTH motif as do positive control mutations in lambda repressor.