[대학원 생명과학과 세미나 안내]
연사 : 최규하 박사 (University of Cambridge)
연제 : Meiotic recombination initiation hotspots in Arabidopsis genes and recomposons
일시 : 2016년 7월 26일 (화) 오후 4시
장소 : 하나과학관 A동 207호
초청교수 : 김옥매 교수
Abstract
Homologous recombination in meiosis produces crossovers or non-crossovers, contributing to genome diversity. Meiotic crossovers are suppressed in eukaryotic heterochromatin and centromeres for genome integrity. However, the extent to which recombination initiates in heterochromatin, but enters non-crossover repair has been unclear. To address this question we generate high-resolution genomic maps of meiotic DNA double strand breaks (DSBs) sites by sequencing oligonucleotides bound to the endogenous SPO11-1 meiotic nuclease in Arabidopsis. We observe strong enrichment of SPO11-1 oligonucleotides (SPO11-1-oligos) in nucleosome-free, AT-rich regions in gene promoters, introns and terminators, consistent with opportunistic cutting that is limited by chromatin organization. Consistently the mutation in ARP6, a subunit of SWR1 chromatin remodelling complex depositing H2A.Z-H2B dimer into nucleosome cause increased nucleosome occupancy and suppressed SPO11-1-oligos at DSBs hotspots. Surprisingly, we find a large family of DNA transposons (Helitrons, MuDR, Tc1, Pogo, Mariner) that are nucleosome depleted, AT-rich and are SPO11-1-oligo hotspots, which we term recomposons. Disrupting epigenetic maintenance of DNA methylation and histone H3K9me2leadstoincreasedSPO11-1-oligoswithincentromericregions,includinginabundantGypsyretroelementsinmet1 and suvh456 mutant. In contrast, SPO11-1-oligos decrease in recomposons in these epigenetic mutants, implying compensatory interactions. Together this reveals unexpected complexity in the Arabidopsis meiotic recombination initiation landscape in genes and transposons. Our findings of recomposons demonstrate a novel role for repetitive elements in genome evolution, via promotion of endogenous meiotic recombination.