Project description:We investigated the genome-wide distribution of Okazaki fragments in the commonly used laboratory Saccharomyces cerevisiae strain S288C to study the DNA replication model adopted by the budding yeast. The method based upon lambda exonuclease digestion for purification of RNA-primed replication intermediates was first improved to be suitable for the purification of Okazaki fragments. Then, we used this improved method to purify Okazaki fragments from S288C yeast cells, followed by Illumina sequencing. We found that the expected asymmetric distribution of Okazaki fragments around confirmed replication origins, which was derived from the semi-discontinuous DNA replication model, was not observed on S. cerevisiae chromosomes. Even around two highly efficient replication origins, ARS522 and ARS416, the ratios of Okazaki fragments on both strands were inconsistent with the semi-discontinuous DNA replication model. Our study supported the discontinuous DNA replication model. Besides, we also observed that Okazaki fragments were overpresented in the transcribed regions in S. cerevisiae mitochondrial genome, which indicated the interplay between transcription and DNA replication.
Project description:Genome wide mapping of RNA polymearase III binding sites in Saccharomyces cerevisiae under normal growth and nutrient starved condition using ChIP-seq. Chromatin Immuno-precipitation (ChIP) was performed for FLAG tagged version of pol III subunit RPC128 after crosslinking the log-phase cells with formaldehyde. MOCK and IP DNA was sequenced and coverage of pol III was calculated at each base of the genome.
Project description:To maintain genomic stability, re-initiation of eukaryotic DNA replication within a single cell cycle is blocked by multiple mechanisms that inactivate or remove replication proteins after G1 phase. Consistent with the prevailing notion that these mechanisms are redundant, we previously showed that simultaneous deregulation of three replication proteins, ORC, Cdc6 and Mcm2-7, was necessary to cause detectable bulk re-replication in G2/M phase in Saccharomyces cerevisiae. In this study, we used microarray comparative genomic hybridization (CGH) to provide a more comprehensive and detailed analysis of re-replication. This genome-wide analysis suggests that re-initiation in G2/M phase primarily occurs at a subset of both active and latent origins, but is independent of chromosomal determinants that specify the use and timing of these origins in S phase. We demonstrate that re-replication can be induced within S phase, but differs in amount and location fr om re-replication in G2/M phase, illustrating the dynamic nature of DNA replication controls. Finally, we show that very limited re-replication can be detected by microarray CGH when only two replication proteins are deregulated, suggesting that the mechanisms blocking re-replication are not redundant. Therefore we propose that eukaryotic re-replication at levels below current detection limits may be more prevalent and a greater source of genomic instability than previously appreciated. Keywords: comparative genomic hybridization (CGH), DNA replication, re-replication
Project description:We investigated the genome-wide distribution of Okazaki fragments in the commonly used laboratory Saccharomyces cerevisiae strain S288C to study the DNA replication model adopted by the budding yeast. The method based upon lambda exonuclease digestion for purification of RNA-primed replication intermediates was first improved to be suitable for the purification of Okazaki fragments. Then, we used this improved method to purify Okazaki fragments from S288C yeast cells, followed by Illumina sequencing. We found that the expected asymmetric distribution of Okazaki fragments around confirmed replication origins, which was derived from the semi-discontinuous DNA replication model, was not observed on S. cerevisiae chromosomes. Even around two highly efficient replication origins, ARS522 and ARS416, the ratios of Okazaki fragments on both strands were inconsistent with the semi-discontinuous DNA replication model. Our study supported the discontinuous DNA replication model. Besides, we also observed that Okazaki fragments were overpresented in the transcribed regions in S. cerevisiae mitochondrial genome, which indicated the interplay between transcription and DNA replication. Examination of the distribution of Okazaki fragments in Saccharomyces cerevisiae strain S288C.
Project description:We report the genome-wide localization of Sgo1p in mitosis of Saccharomyces cerevisiae using ChIP-seq. The high resolution mapping clearly shows a tripartite domain of Sgo1p in each mitotic chromosome. This domain requires the wildtype tension sensing motif (TSM) of histone H3.
Project description:DNA replication must be tightly controlled during each cell cycle to prevent unscheduled replication and ensure proper genome maintenance. The currently known controls that prevent re-replication act redundantly to inhibit pre-Replicative Complex (pre-RC) assembly outside of the G1 phase of the cell cycle. We have analyzed the effects of re-replication on the S. cerevisiae genome using a combination of Comparitive Genomic Hybridization (CGH) of re-replicating strains and Genome-Wide Location Analysis of pre-RC components. These data indicate which sites in the genome assemble pre-RCs under re-replication conditions, which sites undergo re-initiation and the extent of re-replication. Keywords: comparative genomic hybridization, ChIP-chip, re-replication, DNA replication, pre-RC
Project description:Genome wide mapping of RNA polymearase III binding sites in Saccharomyces cerevisiae under normal growth and nutrient starved condition using ChIP-seq. Chromatin Immuno-precipitation (ChIP) was performed for FLAG tagged version of pol III subunit RPC128 after crosslinking the log-phase cells with formaldehyde. MOCK and IP DNA was sequenced and coverage of pol III was calculated at each base of the genome. RPC128-FLAG ChIP-seq single end seqquencing on Illumina GAII. 2 replicates of IP samples and 1 MOCK sample. Done in under normal growth and nutrient deprivation (4 hours).