RESUMEN
In search of genes possibly involved in the regulation of hindbrain segmentation, we have isolated mouse cDNA clones corresponding to putative protein kinase genes by polymerase chain reaction amplification of cDNA from 9.5-day-old embryo hindbrains. In situ hybridization analysis revealed that one of these genes, Sek, was expressed in an alternating segment-restricted pattern in the developing hindbrain. Isolation and analysis of Sek cDNAs covering the entire coding sequence indicated that Sek encoded a putative receptor protein tyrosine kinase, belonging to the Eph family. These data are consistent with a role of the Sek gene product in a signal transduction process involved in pattern formation in the hindbrain.
Asunto(s)
Proteínas Fetales/genética , Regulación Enzimológica de la Expresión Génica , Proteínas de la Membrana/genética , Proteínas del Tejido Nervioso/genética , Proteínas Tirosina Quinasas/genética , Receptores de Superficie Celular/genética , Rombencéfalo/enzimología , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Embrión de Mamíferos , Hibridación in Situ , Ratones , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos , Reacción en Cadena de la Polimerasa/métodos , ARN/genética , ARN/aislamiento & purificación , Receptor EphA4 , Receptor EphA8 , Rombencéfalo/embriología , Homología de Secuencia de AminoácidoRESUMEN
We report here part of the genomic sequence of the mouse homolog of the human gene encoding the transcription factor Sp1. This gene belongs to a subfamily of zinc finger proteins, which includes another transcription factor, Krox-20. The analysis of the mouse Sp1 nucleotide sequence revealed that (i) the C-terminal part of the protein is conserved between man and mouse, consistent with a possible role in transcriptional activation; (ii) while the there Krox-20 zinc fingers are encoded by a unique exon, an intron separates the regions encoding fingers 2 and 3 of Sp1. On the basis of this latter observation, we propose a model for the evolution of the Sp1/Krox-20 gene family which might shed some light on the role of introns in the evolution of modular proteins.
Asunto(s)
Proteínas de Unión al ADN/genética , Factor de Transcripción Sp1/genética , Factores de Transcripción/genética , Células 3T3 , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Evolución Biológica , Proteína 2 de la Respuesta de Crecimiento Precoz , Humanos , Ratones , Datos de Secuencia Molecular , Homología de Secuencia de Ácido Nucleico , Dedos de Zinc/genéticaAsunto(s)
Cromatina/ultraestructura , Replicación del ADN , ADN Viral/genética , Histonas/metabolismo , Poliomavirus/genética , Virus 40 de los Simios/genética , Acetilación , Animales , Secuencia de Bases , Línea Celular , Transformación Celular Viral , Genes Virales , Ratones , Nucleosomas/ultraestructura , Teratoma , Replicación ViralAsunto(s)
Factores de Iniciación de Péptidos , Ribosomas , Antibacterianos/farmacología , Sitios de Unión , Centrifugación por Gradiente de Densidad , Cromatografía en Gel , Cromatografía por Intercambio Iónico , Escherichia coli , Marcaje Isotópico , Magnesio/farmacología , Iniciación de la Cadena Peptídica Traduccional/efectos de los fármacos , Factores de Iniciación de Péptidos/aislamiento & purificación , Ribosomas/efectos de los fármacos , Isótopos de AzufreRESUMEN
The four core histones (H2a, H2b, H3, and H4) bound to simian virus 40 minichromosomes isolated from infected cells contain rapidly labeled acetyl groups in internal positions of the histone polypeptide chain. Upon chase, these acetyl residues decay with a half-life of less than 15 min. The acetyl groups are incorporated in histones bound to mature chromosomes and not in newly synthesized histones bound to replicating viral chromosomes. The rate of acetate incorporation is not related to the degree of steady state acetylation of the individual viral or cellular histones. This rate is 4-fold higher for the viral chromatin than for its cellular counterpart isolated from the same nuclei. The possible role for histone acetylation in viral genome expression is discussed.
Asunto(s)
Cromosomas/metabolismo , Histonas/metabolismo , Virus 40 de los Simios/metabolismo , Acetilación , Línea Celular , ADN/metabolismo , ADN Viral/metabolismo , Cinética , Replicación ViralRESUMEN
The assembly of newly synthesized histones into nucleosomes during replication of SV40 minichromosomes in vivo was studied. Infected cells were labeled with 35S-methionine for a time shorter than that required to complete a round of viral DNA replication. Mature and replicating SV40 minichromosomes were extracted and separated by zonal sedimentation, and their histone content was analyzed by polyacrylamide gel electrophoresis (SDS and acidic urea). We show that the pulse-labeled histones associate preferentially with the replicating DNA.
Asunto(s)
Cromatina/metabolismo , Replicación del ADN , Histonas/metabolismo , Virus 40 de los Simios/metabolismo , Replicación Viral , Línea Celular , Desoxirribonucleoproteínas/metabolismo , Histonas/biosíntesisRESUMEN
We established quail clonal heart muscle cell lines from cardiac rhabdomyosarcomas developed in embryos injected in ovo with the MC29 virus containing the v-myc oncogene. These clones were characterized by means of antibodies detecting markers of striated muscle cells. Two clones were selected for further characterization on the basis of a distribution of myogenic markers similar to that in normal early embryonic cardiac muscle cells. However, these muscle markers progressively disappeared with time in culture. Cardiomyocytic differentiation could be reinduced in culture, by associating the avain cardiac cells with 3T3 cells in a defined synthetic medium. Muscle markers were then reexpressed in all cardiac cells as soon as Day 1 after coculture. Multiplication of cardiac cells continued at the same time. This is characteristic of cardiac clones since MC29-infected quail myoblasts and MC29-infected quail fibroblasts exhibited a split response to 3T3 association, i.e., decreased growth and enhanced differentiation. The cardiac clones were maintained in vitro for more than 60 generations (6 months) without morphological changes. To our knowledge, this is the first description of clonal embryonic avian heart cell lines.