RESUMO
Completing the molecular analysis of the six pal genes of the ambient pH signal transduction pathway in Aspergillus nidulans, we report the characterization of palC and palH. The derived translation product of palH contains 760 amino acids with prediction of seven transmembrane domains in its N-terminal moiety. Remarkably, a palH frameshift mutant lacking just over half the PalH protein, including almost all of the long hydrophilic region C-terminal to the transmembrane domains, retains some PalH function. The palC-derived translation product contains 507 amino acids, and the null phenotype of a frameshift mutation indicates that at least one of the C-terminal 142 residues is essential for function. Uniquely among the A. nidulans pH-signalling pal genes, palC appears to have no Saccharomyces cerevisiae homologue, although it does have a Neurospora crassa expressed sequence tag homologue. In agreement with findings for the palA, palB and palI genes of this signalling pathway, levels of the palC and palH mRNAs do not appear to be pH regulated.
Assuntos
Aspergillus nidulans/genética , Aspergillus nidulans/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Transdução de Sinais , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Mutação da Fase de Leitura , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Transcrição GênicaRESUMO
The zinc finger regions of the Aspergillus nidulans PacC transcription factor, mediating regulation of gene expression by ambient pH, and the Saccharomyces cerevisiae Rim1p transcription factor, mediating control of meiosis and invasiveness, are homologous and both transcription factors undergo proteolytic processing of the C-terminus for conversion to the functional form. In both cases, functioning of a signal transduction pathway involving several gene products is a necessary prerequisite for processing. We now show that the Aspergillus PalI pH signal transduction component is homologous to the Saccharomyces Rim9p meiotic signal transduction component throughout a region containing four hydrophobic, putative membrane-spanning segments. This suggests that PalI might be a membrane sensor for ambient pH. Deletion of the palI gene established that the less extreme phenotype of palI mutations compared with mutations in the other five genes of the pH signalling pathway is a general feature of palI mutations.
Assuntos
Aspergillus nidulans/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Meiose , Proteínas de Membrana , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Transdução de Sinais , Sequência de Aminoácidos , Aspergillus nidulans/metabolismo , Sequência de Bases , Northern Blotting , Clonagem Molecular , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Desoxirribonucleases de Sítio Específico do Tipo II/genética , Desoxirribonucleases de Sítio Específico do Tipo II/metabolismo , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Mutação , Proteínas Repressoras , Saccharomyces cerevisiae/metabolismo , Homologia de Sequência de Aminoácidos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
We have cloned the palA gene of Aspergillus nidulans, one of six genes participating in ambient pH signal transduction in a regulatory circuit mediating pH regulation of gene expression. The derived 798-residue PalA protein is 29.4% identical over its entire length to a hypothetical protein from the nematode Caenorhabditis elegans and also has possible yeast homologs.