RESUMO
A cDNA clone encoding COUP transcription factor, a member of the steroid/thyroid receptor superfamily, has been isolated from a Xenopus neurula (stage 17 embryo) library. Sequencing of this clone reveals an open reading frame encoding a 397 amino acid protein. The amino acid sequence of Xenopus COUP has been compared with its human and Drosophila homologues showing that there are few similarities within the amino-terminal region, whereas the remainder of the protein, including the putative DNA and ligand binding domains, is very well conserved.
Assuntos
Proteínas de Ligação a DNA/genética , Expressão Gênica , Fatores de Transcrição/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Fator I de Transcrição COUP , Clonagem Molecular , DNA/genética , Embrião não Mamífero , Dados de Sequência Molecular , Alinhamento de Sequência , XenopusRESUMO
A cDNA clone encoding the NGFI-B transcription factor, a growth factor inducible member of the steroid/thyroid receptor superfamily, has been isolated from a Xenopus neurula (stage 17 embryo) library. Sequencing of this clone reveals an open reading frame encoding a 577 amino acid protein. Comparisons with its counterparts in rat, mouse and human show that the Xenopus protein has a well conserved DNA binding domain whereas homology in the carboxy terminal region, which includes the putative ligand binding domain, is lower than that typically observed in members of the steroid/thyroid receptor superfamily. This relative lack of homology suggests that, in Xenopus, the as-yet uncharacterized ligand may have subtle distinctions from its mammalian counterparts.
Assuntos
Proteínas de Ligação a DNA/genética , Fatores de Transcrição/genética , Xenopus/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , Dados de Sequência Molecular , Membro 1 do Grupo A da Subfamília 4 de Receptores Nucleares , Receptores Citoplasmáticos e Nucleares , Receptores de Esteroides , Homologia de Sequência de Aminoácidos , Xenopus/embriologiaRESUMO
COUP-TFs (Chicken Ovalbumin Upstream Promoter Transcription Factors) have been proposed to be negative regulators of retinoid receptor-mediated transcriptional activation. In a previous paper we reported the cloning of a Xenopus (x) COUP-TF (Matharu, P.J. and Sweeney, G.E. (1992) Biochim. Biophys. Acta 1129, 331-334). Here we describe the cloning of a second xCOUP-TF. Amino acid sequence comparison between these two Xenopus COUP-TFs revealed a high level of similarity. Extensive amino acid sequence conservation was found among all Drosophila, Xenopus, zebrafish and mammalian COUP-TF genes examined. Phylogenetic tree analyses indicate that the vertebrate COUP-TFs fall into three classes. The two Xenopus COUP-TF genes show similar temporal expression patterns: both are expressed from the end of gastrulation. In situ hybridization studies reveal complex expression patterns in the developing central nervous system (CNS), besides expression in the eye and in some mesodermal tissues. Retinoic acid (RA) treatment enhances xCOUP-TF-A expression in neurula stage embryos, whereas the expression of xCOUP-TF-B is inhibited during the same developmental period. The strictly conserved amino acid sequences and the strong similarities between the expression patterns of the two different xCOUP-TFs on the one hand, and other vertebrate COUP-TF homologues on the other, make it likely that COUP-TFs have a conserved role in patterning the nervous system.
Assuntos
Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Fatores de Transcrição/genética , Tretinoína/farmacologia , Sequência de Aminoácidos , Animais , Fator I de Transcrição COUP , Clonagem Molecular , DNA Complementar , Humanos , Dados de Sequência Molecular , Filogenia , Rombencéfalo/metabolismo , Especificidade da Espécie , Fatores de Tempo , Xenopus/genéticaRESUMO
After the U53 gene encoding the proteinase from human herpesvirus 6 (HHV-6) was sequenced, it was expressed in Escherichia coli, and the activity of the purified, recombinant HHV-6 proteinase was characterized quantitatively by using synthetic peptide substrates mimicking the release and maturation cleavage sites in the polyprotein precursors of HHV-6, human cytomegalovirus (CMV), murine CMV, and Epstein-Barr virus. Despite sharing 40% identity with other betaherpesvirus proteinases such as human CMV proteinase, the one-chain HHV-6 enzyme was distinguished from these two-chain proteinases by the absence of an internal autocatalytic cleavage site.