RESUMO
Maintenance of the correct level and organisation of nucleosomes is crucial for genome function. Here, we uncover a role for a conserved bromodomain AAA-ATPase, Abo1, in the maintenance of nucleosome architecture in fission yeast. Cells lacking abo1(+) experience both a reduction and mis-positioning of nucleosomes at transcribed sequences in addition to increased intragenic transcription, phenotypes that are hallmarks of defective chromatin re-establishment behind RNA polymerase II. Abo1 is recruited to gene sequences and associates with histone H3 and the histone chaperone FACT. Furthermore, the distribution of Abo1 on chromatin is disturbed by impaired FACT function. The role of Abo1 extends to some promoters and also to silent heterochromatin. Abo1 is recruited to pericentromeric heterochromatin independently of the HP1 ortholog, Swi6, where it enforces proper nucleosome occupancy. Consequently, loss of Abo1 alleviates silencing and causes elevated chromosome mis-segregation. We suggest that Abo1 provides a histone chaperone function that maintains nucleosome architecture genome-wide.
Assuntos
Adenosina Trifosfatases/metabolismo , Cromatina/genética , Cromatina/metabolismo , Nucleossomos/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Adenosina Trifosfatases/química , Adenosina Trifosfatases/genética , Montagem e Desmontagem da Cromatina , Proteínas Cromossômicas não Histona/metabolismo , Segregação de Cromossomos , DNA Intergênico , Inativação Gênica , Chaperonas de Histonas/genética , Chaperonas de Histonas/metabolismo , Histonas/genética , Histonas/metabolismo , Nucleossomos/genética , Regiões Promotoras Genéticas , RNA Polimerase II/genética , Proteínas de Schizosaccharomyces pombe/química , Proteínas de Schizosaccharomyces pombe/genética , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
Checkpoints monitor the successful completion of cell cycle processes, such as DNA replication, and also regulate the expression of cell cycle-dependent genes that are required for responses. In the model yeast Schizosaccharomyces pombe G 1/S phase-specific gene expression is regulated by the MBF (also known as DSC1) transcription factor complex and is also activated by the mammalian ATM/ATR-related Rad3 DNA replication checkpoint. Here, we show that the Yox1 homeodomain transcription factor acts to co-ordinate the expression of MBF-regulated genes during the cell division cycle. Moreover, our data suggests that Yox1 is inactivated by the Rad3 DNA replication checkpoint via phosphorylation by the conserved Cds1 checkpoint kinase. Collectively, our data has implications for understanding the mechanisms underlying the coordination of cell cycle processes in eukaryotes.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Ciclo Celular , Replicação do DNA , Regulação Fúngica da Expressão Gênica , Proteínas de Homeodomínio/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Fatores de Transcrição/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia , Proteínas de Ciclo Celular/genética , Quinase do Ponto de Checagem 2 , DNA Fúngico/genética , DNA Fúngico/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Homeodomínio/genética , Fosforilação , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Schizosaccharomyces/citologia , Proteínas de Schizosaccharomyces pombe/genética , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
Schizosaccharomyces pombe utilizes two opposing signaling pathways to sense and respond to its nutritional environment. Glucose detection triggers a cyclic AMP signal to activate protein kinase A (PKA), while glucose or nitrogen starvation activates the Spc1/Sty1 stress-activated protein kinase (SAPK). One process controlled by these pathways is fbp1+ transcription, which is glucose repressed. In this study, we isolated strains carrying mutations that reduce high-level fbp1+ transcription conferred by the loss of adenylate cyclase (git2delta), including both wis1- (SAPK kinase) and spc1- (SAPK) mutants. While characterizing the git2delta suppressor strains, we found that the git2delta parental strains are KCl sensitive, though not osmotically sensitive. Of 102 git2delta suppressor strains, 17 strains display KCl-resistant growth and comprise a single linkage group, carrying mutations in the cgs1+ PKA regulatory subunit gene. Surprisingly, some of these mutants are mostly wild type for mating and stationary-phase viability, unlike the previously characterized cgs1-1 mutant, while showing a significant defect in fbp1-lacZ expression. Thus, certain cgs1- mutant alleles dramatically affect some PKA-regulated processes while having little effect on others. We demonstrate that the PKA and SAPK pathways regulate both cgs1+ and pka1+ transcription, providing a mechanism for cross talk between these two antagonistically acting pathways and feedback regulation of the PKA pathway. Finally, strains defective in both the PKA and SAPK pathways display transcriptional regulation of cgs1+ and pka1+, suggesting the presence of a third glucose-responsive signaling pathway.