Structure and evolution of four POU domain genes expressed in mouse brain.

Abstract

Four mouse POU domain genomic DNA clones-Brain-i, Brain-2, Brain-4, and Scip-and Bran-2 cDNA, which are expressed in adult brain, were cloned and the coding and noncoding regions ofthe genes were sequenced. The amino acid sequences of the four PoU domains are highly conserved; sequences in other regions of the proteins also are conserved but to a lesser extent. The absence of introns from the coding regions of the four POU domain genes and the similarity of amino acid sequences of the corresponding proteins suggest that the coding region of the ancestral class HI POU domain gene lacked introns and therefore may have originated by reverse transcription of a molecule of POU domain mRNA followed by insertion ofthe cDNA into germ cell genomic DNA. Additional duplications ofthe ancestral class HI POU domain gene (or mRNA) would create the Brain-i, Brain-2, Brain-4, and Scip genes.POU domain proteins bind to specific nucleotide sequences in DNA and regulate gene expression (for reviews, see refs. 1 and 2). The POU domain is a conserved amino acid sequence =150 amino acid residues long. The initial region of 69-72 amino acid residues is termed the POU-specific domain, which is followed by a 15-to 25-amino acid residue linker region and a 60-amino acid residue POU homeodomain. Both the POU-specific domain and the homeodomain are required for specific high-affinity binding to DNA (3, 4).Rosenfeld and his colleagues have sorted POU domains into different groups on the basis of POU domain amino acid sequence similarity (2). Three mammalian class III POU domain cDNAs have been described-human (5) and rat (2) Brain-i and Brain-2 and rat (5-8) and mouse (9-11) Scip (also termed Oct-6 and Tst-J)-that have closely related POU domains and are expressed in embryonic and adult brain. Only the POU domain regions of human and rat Brain-i and Brain-2 cDNA have been sequenced thus far (2, 5), whereas the complete coding sequences of rat (6-8) and mouse (9-11) Scip cDNA have been reported. Scip RNA is expressed in a subset of neurons, oligodendroglia, Schwann cells, and in the testis (5-11). The expression of the Scip gene is promoted by cAMP (6, 7).In this report, a fourth class III mouse POU domain gene, Brain4, is described, which is also expressed in adult mouse brain. Brain4 is similar to the recently reported XLPOU 2 POU domain partial cDNA of Xenopus laevis (12). Three additional mouse class III POU domain genomic clonesBrain-i, Brain-2, and Scip-and Brain-2 cDNA were obtained and the nucleotide sequences of the coding and noncoding regions were determined. Comparison of the deduced amino acid sequences of the four POU domain proteins shows that the structure of the genes and the amino Fig. 4). DNA inserts were subcloned in pBluescript II SK+ and KS+. The nucleotide sequences of both strands of DNA were determined with universal or specific oligodeoxynucleotide primers and single-stranded DNA templates by the dideoxynucleotide chain-termination method (13).OlUgdeoxynucleotide Probes. Four oligodeoxynucleotides (48 bases...

The prepattern transcription factor Irx3 directs nephron segment identity

“…BU703212), Irx2 (BI111057), Irx3 (BI525434), Irx4 (BE367799), Irx5 (Bosse et al 2000), and Irx6 (Peters et al 2000). For probe synthesis, the mouse Brn1 cDNA (Hara et al 1992) was subcloned by PCR into pGEM-TEasy (Promega).…”

qBrain-2, a POU domain gene expressed in quail embryos

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