Project description:Extrachromosomal DNA (ecDNA) is an important carrier for the amplification of proto-oncogenes. It can not only drive cancer progression by increasing the copy number of oncogenes but also influence the transcriptional regulation of oncogenes by increasing chromatin accessibility and regulating chromatin interactions. Currently, the generation of ecDNA is rather complex and the exact mechanism remains unclear. This study aims to investigate the molecular mechanism underlying the generation of ecDNA in order to identify the targets for ecDNA-targeted drug therapies. We analyzed the chromatin landscape in COLO320-DM and COLO320-HSR cells through CUT&Tag. The results of CUT&Tag for Lig3, the open chromatin marker H3K27ac, and the promoter marker H3K4me3 showed that Lig3 was specifically enriched in the MYC ecDNA amplification regions and bound to a large number of open chromatin regions and promoter regions, indicating that Lig3 may be related to the formation of ecDNA and stably bind to ecDNA, thereby maintaining the integrity of the genes carried by ecDNA. Furthermore, we found that there were a large number of merge peaks between Lig3 and YY1 across the whole genome, which were abundantly occupied at the MYC ecDNA amplification sites. Meanwhile, we observed that in COLO320-DM cells (where oncogenes are amplified in the form of ecDNA), there was a significant enrichment of YY1 in the MYC amplification regions, while in COLO320-HSR cells (where oncogenes are amplified on the homogeneously staining regions, HSR), the peaks of YY1 were significantly decreased. Our data suggest that YY1 is essential for the generation of ecDNA. It forms a complex with Lig3 to jointly regulate the formation of ecDNA, and this complex can be detected as it resides on ecDNA for a relatively long period of time. This may also be related to the stability of ecDNA and its involvement in genomic regulation.
Project description:YY1 is a widely expressed transcriptional regulatory factor that is overexpressed in various cancer types, promoting the expression of numerous oncogenes and contributing to cancer progression. It has been identified as a significant biomarker of cancer, correlating with poor prognosis in cancer patients. Moreover, YY1 is an essential regulator of DNA looping, preferentially occupying enhancers and promoters. YY1-mediated enhancer-promoter loops participate in various cancer-related biological functions by regulating gene expression. The circular nature of ecDNA suggests that its formation involves a DNA looping process. Notably, in tumor cells, YY1-mediated DNA looping is closely associated with the activation of multiple oncogenes and immunosuppressive genes, resembling the types of genes carried by ecDNA. Therefore, we investigated the link between DNA looping mediated by YY1 and ecDNA generation. We conducted YY1 HiCUT in COLO320-DM/HSR cells. We found that in COLO320-DM cells, a large number of YY1-mediated loops were located in the MYC amplification region, while only 1% of these loops were observed in the same region in COLO320-HSR cells. The result indicates YY1 mediates DNA looping through dimerization in cells has potential correlation with ecDNA biogenesis.
Project description:To investigate YY1 and ZFP384 binding in microglia and the microglial cell line after ischemic stroke, we performed cleavage under targets and tagmentation (CUT&Tag) analysis using anti-YY1 and anti-ZFP384 antibodies.
Project description:Extrachromosomal DNAs (ecDNAs) play an important role in tumor progression. ecDNA hubs have been shown to be anchored by BRD4, a chromatin reader. However, the epigenetic regulation of ecDNA hub biogenesis remains unknown. Here we show that histone 3 lysine 56 acetylation (H3K56ac) mark binds to BRD4 specifically. Analysis of ChIP-seq datasets showed that both H3K56ac and H3K27ac co-occupied with BRD4 binding at the ecDNA-chromosome interaction sites and ecDNA itself.
Project description:R-loops are three-stranded nucleic acid structures consisting of a DNA-RNA hybrid and a displaced single-stranded DNA (ssDNA). R-loops are facilitators of gene expression and genome stability that play both regulatory and potentially deleterious roles in cells. To elucidate the protein-based mechanisms of R-loop regulation, we developed an APEX-based proximity proteomics using a catalytically inactive mutant of RNase H1 (APEX-RNH1D210N) to profile the proximal proteome of R-loops in cells. Our proteomics results identified a list of known and potential R-loop-binding proteins with diverse molecular functions, and confirmed YY1 as a novel R-loop-binding protein through a series of in-vitro binding assays. YY1 is a DNA-binding protein recognizing a consensus motif or G-quadruplex (G4) structure. Our binding results indicated YY1's notably stronger affinity for R-loops compared to RNA/DNA hybrid, DNA G4 and DNA without a consensus motif, implying R-loops' role in YY1 recruitment to genomic regions lacking a YY1-binding motif. To investigate YY1-R-loop interaction in cells, we introduced R-loop structures into specific genomic regions vis CRISPR-dCas9 targeting, followed by DRIP-qPCR, YY1-ChIP-qPCR and RT-qPCR experiments. Increased R-loop levels corresponded with heightened YY1 occupancy and differential gene expression, suggesting YY1-R-loop interactions contribute to transcriptional regulation. More importantly, our RNA-seq and YY1-ChIP-seq results revealed that the interactions between YY1 and promoter R-loops were involved in global transcriptional regulation, especially in the positive regulation of transcription. Together, we identified YY1 as a novel R-loop-binding protein and uncovered a mechanism wherein YY1-R-loop interactions regulate gene expression.
Project description:The protein Yin-Yang 1 (YY1) is a ubiquitous multifunctional transcription factor. Interestingly, there are several cellular functions controlled by YY1 that could play a role in Leishmania pathogenesis. Leishmaniasis is a human disease caused by protozoan parasites of the genus Leishmania. This study examined the potential role of macrophage YY1 in promoting Leishmania intracellular survival. Knockdown of YY1 resulted in attenuated survival of Leishmania in infected macrophages, suggesting a role of YY1 in Leishmania persistence. Biochemical fractionation studies revealed Leishmania infection caused redistribution of YY1 to the cytoplasm from the nucleus where it is primarily located. Inhibition of nuclear transport by leptomycin B attenuates infection-mediated YY1 redistribution and reduces Leishmania survival. This suggests that Leishmania induces the translocation of YY1 from the nucleus to the cytoplasm of infected cells, where it may regulate host molecules to favour parasite survival. A label-free quantitative whole proteome approach showed that the expression of a large number of macrophage proteins was dependent on the YY1 level. Interestingly, several of these proteins were modulated in Leishmania-infected cells, revealing YY1-dependent host response and suggesting their potential role in Leishmania pathogenesis. Together, these findings identify YY1 as a novel and essential virulence factor by proxy that promotes Leishmania survival.