Project description:DDX39A and DDX56 recombinant proteins were assayed using commercial protein microarrays in order to detect potential interaction partners.
Project description:DEAD box RNA helicase DDX39A has been shown to regulate RNA metabolism; however its role in vertebrate development has not previously been examined. To determine the impact of loss of ddx39a on transcriptome during vertebrate early development, we pursued transcriptome analysis (RNA-Seq) on wild type and ddx39a mutant zebrafish embryos at 24 hour-post-fertilization. And by using RIP-seq to identify targeted RNA which were DDX39A binded.
Project description:Dead-box RNA helicases are crucial in mRNA processing, specifically in RNA splicing. Our previous work has shown that DDX39B is responsible for regulating the splicing of IL7R exon 6 and several FOXP3 introns, which rely on DDX39B's helicase and ATPase activities, respectively [this is not accurate since exon 6 also must require the ATPase activity, which is required for helicase activity]. In this study, we aimed to investigate whether DDX39A, a highly homologous paralog of DDX39B, plays a similar role in regulating alternative RNA splicing. We find that DDX39A and DDX39B have significant redundancy in their gene targets, however, DDX39A is incapable of complementing defective splicing of IL7R exon 6 when DDX39B is knockdown. Conversely, overexpressing DDX39A can rescue FOXP3 intron 11 splicing under DDX39B-depleted conditions. In this work we also confirm that introns containing C-rich/U-poor polypyrimidine tract are very sensitive to DDX39B levels. We also observed that cassette exons with C-rich/U-poor py tracts in upstream introns were also sensitive to DDX39B levels and were skipped more upon depletion of DDX39B, but not DDX39A. Among the introns retained more upon DDX39A and DDX39B depletion were DDX39A and DDX39B intron 6, which depend on DDX39A and DDX39B levels, respectively. Therefore, we identified an autoregulatory mechanism through which DDX39A and DDX39B control their respective expression. This study presents evidence that while DDX39A and DDX39B differentially impact certain RNA splicing events, they have many shared targets.
Project description:Histone variant H2A.Z is a critical player in setting up the chromatin environment that mediates transcription and other activities on chromatin. However, how H2A.Z is incorporated to specific chromatin regions is not clear. To examine the potential role of sequence-specific transcription factors in targeting H2A.Z, we screened for genome-wide H2A.Z-interacting proteins in vivo using a novel technique called bait Protein-Protein Interaction-sequencing (bPPI-seq). Among the hundreds of H2A.Z-interacting proteins identified by bPPI-seq, we show that a zinc-finger transcription factor, Osr1 interacts with H2A.Z both in vitro and in vivo and co-localizes with H2A.Z on chromatin. Knockdown of Osr1 compromised H2A.Z deposition to hundreds of chromatin sites enriched with Osr1 binding motifs. Furthermore, Osr1 and H2A.Z co-regulate the expression of numerous target genes. These results indicate that Osr1 directly interacts with H2A.Z, mediates its incorporation to a large number of target sites and regulates gene expression. Our data indicate that bPPI-seq can be widely applied to identify unbiasedly interacting proteins under physiologic conditions.
Project description:DNA-protein interactions regulate critical biological processes. Identifying proteins that bind to specific, functional genomic loci is essential for understanding the underlying regulatory mechanisms on a molecular level. Here, we describe a novel co-binding-mediated protein profiling (CMPP) strategy to investigate the interactome of DNA G-quadruplexes (G4s) in cellular chromatin. CMPP involves cell-permeable, functionalized G4-ligand probes that bind endogenous G4s and subsequently crosslink to co-binding G4-interacting proteins in situ. We show the robustness of CMPP on proximity labelling of a G4 binding protein in vitro. Employing this approach in live cells, we identify hundreds of putative G4-interacting proteins from various functional classes. Next, we observe high G4 binding affinity and selectivity for several G4 interactors in vitro and confirm direct G4 interactions for one of the top candidates in chromatin. Our studies provide a chemical approach to map protein interactions of specific nucleic acid features in living cells.
Project description:The accurate processing of stalled forks by the DNA2 nuclease is pivotal for replication fork restart, as excessive degradation poses a threat to genomic stability. However, the regulation of DNA2 activity at stalled forks remains elusive. Here, we demonstrate that, upon replication stress, RNA polymerase II (RNAPII) is recruited to stalled forks, actively promoting the transient formation of RNA-DNA hybrids. Furthermore, we provide evidence that DDX39A, functioning as an RNA-DNA resolver, unwinds these hybrids, allowing DNA2 access to stalled forks. This orchestrated process facilitates controlled DNA2-dependent stalled fork processing and restart. Nevertheless, premature removal of RNA-DNA hybrids at stalled forks leads to DNA2-dependent excessive degradation of nascent DNA. Finally, we reveal that loss of DDX39A enhances the protection of stalled forks in BRCA1/2-deficient cells, consequently conferring chemoresistance within this specific cellular context. Our results suggest that the dynamic regulation of RNA-DNA hybrid formation at stalled forks by RNAPII and DDX39A precisely governs the timing of DNA2 activation, contributing to stalled fork processing and restart, ultimately promoting genome stability.
Project description:We have combined biochemical purification of Mediator from chromatin with ChIP-sequencing to reveal Mediator occupupancy to DNA globally and to identify proteins interacting specifically with Mediator in chromatin. We find that Mediator occupy strong chromosomally interacting domain (CID) boundaries and nearly all tRNA genes. Purification of Mediator from chromatin shows that it interacts with proteins and protein complexes that have been shown to interact with CID boundaries such as RSC, Ssu72 and histone H4. We also show specific interaction between Mediator and the Arp2/Arp3, CPF, CF 1A and LSm, complexes in chromatin. These factors are involved in mRNA 3'-end processing, gene looping, actin assembly and mRNA decay.