RESUMEN
Chromatin modification through histone H3 lysine 36 methylation by the SETD2 tumor suppressor plays a key role in maintaining genome stability. Here, we describe a role for Set2-dependent H3K36 methylation in facilitating DNA replication and the transcriptional responses to both replication stress and DNA damage through promoting MluI cell-cycle box (MCB) binding factor (MBF)-complex-dependent transcription in fission yeast. Set2 loss leads to reduced MBF-dependent ribonucleotide reductase (RNR) expression, reduced deoxyribonucleoside triphosphate (dNTP) synthesis, altered replication origin firing, and a checkpoint-dependent S-phase delay. Accordingly, prolonged S phase in the absence of Set2 is suppressed by increasing dNTP synthesis. Furthermore, H3K36 is di- and tri-methylated at these MBF gene promoters, and Set2 loss leads to reduced MBF binding and transcription in response to genotoxic stress. Together, these findings provide new insights into how H3K36 methylation facilitates DNA replication and promotes genotoxic stress responses in fission yeast.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Daño del ADN , Replicación del ADN , N-Metiltransferasa de Histona-Lisina/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/enzimología , Schizosaccharomyces/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Puntos de Control del Ciclo Celular/genética , Daño del ADN/genética , Replicación del ADN/genética , ADN de Hongos/metabolismo , Regulación hacia Abajo/genética , Regulación Fúngica de la Expresión Génica , Genes Fúngicos , Mutación/genética , Nucleótidos/metabolismo , Origen de Réplica/genética , Fase S/genéticaRESUMEN
Expression of a G1/S regulon of genes that are required for DNA replication is a ubiquitous mechanism for controlling cell proliferation; moreover, the pathological deregulated expression of E2F-regulated G1/S genes is found in every type of cancer. Cellular tolerance of deregulated G1/S transcription is surprising because this regulon includes many dosage-sensitive proteins. Here, we used the fission yeast Schizosaccharomyces pombe to investigate this issue. We report that deregulating the MBF G1/S regulon by eliminating the Nrm1 corepressor increases replication errors. Homology-directed repair proteins, including MBF-regulated Ctp1(CtIP), are essential to prevent catastrophic genome instability. Surprisingly, the normally inconsequential MBF-regulated S-phase cyclin Cig2 also becomes essential in the absence of Nrm1. This requirement was traced to cyclin-dependent kinase inhibition of the MBF-regulated Cdc18(Cdc6) replication origin-licensing factor. Collectively, these results establish that, although deregulation of G1/S transcription is well tolerated by cells, nonessential G1/S target genes become crucial for preventing catastrophic genome instability.
Asunto(s)
Puntos de Control de la Fase G1 del Ciclo Celular/genética , Genes Fúngicos , Inestabilidad Genómica , Regulón , Schizosaccharomyces/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Ciclina B/genética , Ciclina B/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Schizosaccharomyces/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
New data on the relationship between two proteins, cyclin D and Rb, suggest that we need to re-evaluate our understanding of how cells enter into the cell cycle.
