Project description:Meiotic recombination 11 (Mre11) is a relatively conserved nuclease in various species. Mre11 plays important roles in meiosis and DNA damage repair in yeast, humans and Arabidopsis, but little research has been done on mitotic DNA replication and repair in rice. Here, it was found that Mre11 was an extensively expressed gene among the various tissues and organs of rice, and loss-of-function of Mre11 resulted in severe defects of vegetative and reproductive growth, including dwarf plants, abnormally developed male and female gametes, and completely abortive seeds. The decreased number of cells in the apical meristem and the appearance of chromosomal fragments and bridges during the mitotic cell cycle in rice mre11 mutant roots revealed an essential role of OsMre11. Further research showed that DNA replication was suppressed, and a large number of DNA strand breaks occurred during the mitotic cell cycle of rice mre11 mutants. The expression of OsMre11 was up-regulated with the treatment of hydroxyurea and methyl methanesulfonate. Moreover, OsMre11 could form a complex with OsRad50 and OsNbs1, and they might function together in non-homologous end joining and homologous recombination repair pathways. These results indicated that OsMre11 plays vital roles in DNA replication and damage repair of the mitotic cell cycle, which ensure the development and fertility of rice by maintaining genome stability.
Project description:Entry into and exit from mitosis is driven by precisely-timed changes in protein abundance, and involves transcriptional regulation and protein degradation. However, the role of translational regulation in modulating cellular protein content during mitosis remains poorly understood. Here, using ribosome profiling, we show that translational, rather than transcriptional regulation is the dominant mechanism for modulating protein synthesis at mitotic entry. The vast majority of regulated mRNAs are translationally repressed, which contrasts previous findings of selective mRNA translational activation at mitotic entry. One of the most pronounced translationally repressed genes in mitosis is Emi1, an inhibitor of the anaphase promoting complex (APC), which is degraded during mitosis. We show that Emi1 degradation is insufficient for full APC activation and that simultaneous translational repression is required. These results provide a genome-wide view of protein translation during mitosis and suggest that translational repression may be used to ensure complete protein inactivation Ribosome profiling and mRNA-seq from 3 time points in the cell cycle
Project description:Entry into and exit from mitosis is driven by precisely-timed changes in protein abundance, and involves transcriptional regulation and protein degradation. However, the role of translational regulation in modulating cellular protein content during mitosis remains poorly understood. Here, using ribosome profiling, we show that translational, rather than transcriptional regulation is the dominant mechanism for modulating protein synthesis at mitotic entry. The vast majority of regulated mRNAs are translationally repressed, which contrasts previous findings of selective mRNA translational activation at mitotic entry. One of the most pronounced translationally repressed genes in mitosis is Emi1, an inhibitor of the anaphase promoting complex (APC), which is degraded during mitosis. We show that Emi1 degradation is insufficient for full APC activation and that simultaneous translational repression is required. These results provide a genome-wide view of protein translation during mitosis and suggest that translational repression may be used to ensure complete protein inactivation
Project description:The shugoshin proteins are universal protectors of centromeric cohesin during mitosis and meiosis. The binding of human hSgo1 to the PP2A-B56 phosphatase through a coiled coil (CC) region mediates cohesion protection during mitosis. Here we undertook a structure function analysis of the PP2A-B56-hSgo1 complex, revealing unanticipated aspects of complex formation and function. We establish that a highly conserved pocket on the B56 regulatory subunit is required for hSgo1 binding and cohesion protection during mitosis in human somatic cells. Consistent with this, we show that hSgo1 blocks the binding of PP2A-B56 substrates containing a canonical B56 binding motif. We find that PP2A-B56 bound to hSgo1 dephosphorylates Cdk1 sites on hSgo1 itself to modulate cohesin interactions. Collectively our work provides important insight into cohesion protection during mitosis.
Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region. Examination of H2A.Z duing G0/G1 and mitosis in bladder cancer cells
Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region.
Project description:The apocarotenoid zaxinone promotes growth and suppresses strigolactone biosynthesis in rice. To shed light on the mechanisms underlying its growth promoting effect, we employed a combined omics approach integrating transcriptomics and metabolomics analysis of rice seedlings treated with zaxinone
Project description:The phytohormone cytokinin plays a significant role in nearly all aspects of plant growth and development. Cytokinin signaling has primarily been studied in the dicot model Arabidopsis, with relatively little work done in monocots, which include rice (Oryza sativa) and other cereals of agronomic importance. The cytokinin signaling pathway is a phosphorelay comprised of the histidine kinase receptors (HKs), the authentic histidine phosphotransfer proteins (AHPs), and the type-B Response Regulators (ARRs). Two negative regulators of cytokinin signaling have been identified: the type-A ARRs, which are cytokinin primary response genes, and the pseudo histidine phosphotransfer proteins (PHPs), which lack the His residue required for phosphorelay. Here, we describe the role of the PHP genes from rice. Phylogenic analysis indicates that the PHPs are generally first found in the genomes of gymnosperms and that they arose independently in monocots and dicots. Consistent with this, the three rice PHPs fail to complement an Arabidopsis php mutant (ahp6). Disruption of the three PHPs results in a molecular phenotype consistent with these elements acting as negative regulators of basal cytokinin signaling, including the constitutive up-regulation of a number of type-A RR and cytokinin oxidase genes. The triple php mutant affects multiple aspects of rice growth and development, including shoot morphology, panicle architecture and seed fill. However, in contrast to Arabidopsis, disruption of the rice PHPs does not affect root vascular patterning, suggesting that while many aspects of key signaling networks are conserved between monocots and dicots, the molecular components regulating some processes are distinct.