Project description:Chromatin replication requires tight coordination of nucleosome assembly machinery with DNA replication machinery. While significant progress has been made in characterizing histone chaperones in this process, the mechanism of whereby nucleosome assembly couples with DNA replication remains largely unknown. Here we show that replication protein A (RPA), a single-stranded DNA (ssDNA) binding protein that is essential for DNA replication provides a binding platform for H3-H4 deposition by histone chaperons and is required for nucleosome formation on nascent chromatin. RPA binds free histone H3-H4 but not nucleosomal histones, and a RPA coated ssDNA stimulates assembly of H3-H4 onto double strand DNA in vitro. RPA mutant with reduced H3-H4 binding exhibits synthetic genetic interaction with mutations at key factors involved in replication-coupled (RC) nucleosome assembly, and are defective in assembly of replicating DNA into nucleosomes in cells. These results reveal a novel function for RPA in nucleosome assembly and a mechanism whereby nucleosome assembly is coordinated with DNA replication.
Project description:Porcine 60K BeadChip genotyping arrays (Illumina) are increasingly being applied in pig genomics to validate SNPs identified by re-sequencing or assembly-versus-assembly method. Here we report that more than 98% SNPs identified from the porcine 60K BeadChip genotyping array (Illumina) were consistent with the SNPs identified from the assembly-based method. This result demonstrates that whole-genome de novo assembly is a reliable approach to deriving accurate maps of SNPs.
Project description:The naked mole-rat (NMR; Heterocephalus glaber) has recently gained considerable attention in the scientific community for its unique potential to unveil novel insights in the fields of medicine, biochemistry, and evolution. NMRs exhibit unique adaptations that include protracted fertility, cancer resistance, eusociality, and anoxia. This suite of adaptations is not found in other rodent species, suggesting that interrogating conserved and accelerated regions in the NMR genome will find regions of the NMR genome fundamental to their unique adaptations. However, the current NMR genome assembly has limits that make studying structural variations, heterozygosity, and non-coding adaptations challenging. We present a complete diploid naked-mole rat genome assembly by integrating long-read and 10X-linked read genome sequencing of a male NMR and its parents, and Hi-C sequencing in the NMR hypothalamus (N=2). Reads were identified as maternal, paternal or ambiguous (TrioCanu). We then polished genomes with Flye, Racon and Medaka. Assemblies were then scaffolded using the following tools in order: Scaff10X, Salsa2, 3d-DNA, Minimap2-alignment between assemblies, and the Juicebox Assembly Tools. We then subjected the assemblies to another round of polishing, including short-read polishing with Freebayes. We assembled the NMR mitochondrial genome with mitoVGP. Y chromosome contigs were identified by aligning male and female 10X linked reads to the paternal genome and finding male-biased contigs not present in the maternal genome. Contigs were assembled with publicly available male NMR Fibroblast Hi-C-seq data (SRR820318). Both assemblies have their sex chromosome haplotypes merged so that both assemblies have a high-quality X and Y chromosome. Finally, assemblies were evaluated with Quast, BUSCO, and Merqury, which all reported the base-pair quality and contiguity of both assemblies as high-quality. The assembly will next be annotated by Ensembl using public RNA-seq data from multiple tissues (SRP061363). Together, this assembly will provide a high-quality resource to the NMR and comparative genomics communities.
