RESUMEN
sep1(+), the Schizosaccharomyces pombe homologue of the forkhead/HNF-3 transcription factors, plays a role in the cell separation at the end of mitosis. Its inactivation by interruption of the coding region is not lethal but renders the sister cells unable to separate and causes hyphal growth. The persistence of unsplit septa indirectly interferes with the establishment of new cell polarity by preventing cell growth at cell tips. Temporal changes in the transcription of sep1(+) correlate with the cell cycle progression showing maximal expression at the peak of cell plate index in synchronized cultures. The constitutive overexpression of sep1(+) has no discernible effect on the morphology and physiology of the cells.
Asunto(s)
Mitosis/genética , Schizosaccharomyces/citología , Factores de Transcripción/genética , Polaridad Celular/genética , Pared Celular/metabolismo , Factores de Transcripción Forkhead , Proteínas Nucleares/genética , ARN de Hongos/análisis , ARN Mensajero/análisis , Proteínas Recombinantes/biosíntesis , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe , Eliminación de Secuencia , Homología de Secuencia de Aminoácido , Factores de Transcripción/biosíntesisRESUMEN
sep1+ encodes a Schizosaccharomyces pombe homolog of the HNF-3/forkhead family of the tissue-specific and developmental gene regulators identified in higher eukaryotes. Its mutant allele sep1-1 causes a defect in cytokinesis and confers a mycelial morphology. Here we report on genetic interactions of sep1-1 with the M-phase initiation mutations wee1-, cdc2-1w, and cdc25-22. The double mutants sep1-1 wee1- and sep1-1 cdc2-1w form dikaryon cells at high frequency, which is due to nuclear division in the absence of cell division. The dikaryosis is reversible and suppressible by cdc25-22. We propose that the genes wee1+, cdc2+, cdc25+, and sep1+ form a regulatory link between the initiation of mitosis and the initiation of cell division.
Asunto(s)
Proteínas Nucleares , Proteínas de Saccharomyces cerevisiae , Schizosaccharomyces/citología , Schizosaccharomyces/genética , Actinas/aislamiento & purificación , Proteína Quinasa CDC2/genética , Proteínas de Ciclo Celular/genética , División Celular/genética , Núcleo Celular/genética , Núcleo Celular/ultraestructura , Exorribonucleasas/genética , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Modelos Genéticos , Mutación , Fosfoproteínas Fosfatasas/genética , Proteínas Tirosina Quinasas/genética , Proteínas de Schizosaccharomyces pombe , Esporas Fúngicas , Fosfatasas cdc25RESUMEN
We report on the cloning of sep1+, a gene whose mutation causes filamentous growth in Schizosaccharomyces pombe. Since cell growth and propagation are not affected by the mutation, it could not be cloned using selective conditions for the identification of the positive transformants. Instead, we cloned it from a cosmid of a contig (Hoheisel et al., Cell 73, 109-1120, 1993) supposed to cover the chromosomal region where the sep1-1 mutation mapped. The 1761 bp long ORF codes for a protein containing a sequence similar to the DNA-binding domains of the HNF-3/forkhead family of transcription factors.
Asunto(s)
Proteínas de Unión al ADN/genética , Exorribonucleasas/genética , Proteínas Nucleares/genética , Proteínas de Saccharomyces cerevisiae , Schizosaccharomyces/genética , Homología de Secuencia de Aminoácido , Factores de Transcripción/genética , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , Proteínas de Unión al ADN/química , Exorribonucleasas/química , Factores de Transcripción Forkhead , Regulación del Desarrollo de la Expresión Génica , Datos de Secuencia Molecular , Proteínas Nucleares/química , Schizosaccharomyces/química , Alineación de Secuencia , Factores de Transcripción/químicaRESUMEN
The x-ray fluorescence spectroscopy and the spectrophotometric method were used to determine lead concentrations in the air of an auto repair shop. The calibration of the x-ray spectrometer was performed with known concentrations of water solutions of Pb(NO3)2 on filter paper. Samples were prepared by filtration of measured volumes of air. The lead amounts determined were below the maximum permissible concentrations. The results obtained with the spectrophotometric method are also given showing discrepancies between 10 and 30 per cent if compared with the results of x-ray fluorescence spectroscopy.
