Project description:Both transcription and replication can take place simultaneously on the same DNA template, potentially leading to transcription-replication conflicts (TRCs) and topological problems. Here we asked which topoisomerase(s) is/are the best candidate(s) for sensing TRC. Genome-wide topoisomerase binding sites were mapped in parallel for all the nuclear topoisomerases (TOP1, TOP2A, TOP2B, TOP3A and TOP3B). To increase the signal to noise ratio (SNR), we used ectopic expression of those topoisomerases in H293 cells followed by a modified CUT&Tag method. Although each topoisomerase showed distinct binding patterns, all topoisomerase binding signals positively correlated with gene transcription. TOP3A binding signals were suppressed by DNA replication inhibition. This was also observed but to a lesser extent for TOP2A and TOP2B. Hence, we propose the involvement of TOP3A in sensing both head-on TRCs (HO-TRCs) and codirectional TRCs (CD-TRCs). In which case, the TOP3A signals appear concentrated within the promoters and first 20 kb regions of the 5’ -end of genes, suggesting the prevalence of TRCs and the recruitment of TOP3A in the 5’-regions of transcribed and replicated genes.
Project description:To compare expression profiles in the cardiomyocytes with wild type top2b and those with top2b deletion after in vivo treatment of mice with doxorubicin or drug vehicle Doxorubicin is widely used in modern cancer treatments, despite the advent of targeted therapy. However, a dose-dependent cardiotoxicity often limits its clinical use. The prevailing theory hypothesizes that doxorubicin-induced cardiotoxicity is the result of reactive oxygen species (ROS) generation due to redox-cycling of doxorubicin. Here we showed that cardiomyocyte-specific deletion of Topoisomerase II beta (Top2b) markedly reduced DNA double-strand breaks, apoptosis, and functional damages in doxorubicin-treated hearts. To investigate transcriptomic changes after doxorubicin treatment in wild type mouse and mouse with cardiac specific deletion of Top2b, we examined the expression profiles in 4 groups of mice (3/group), ie. wildtype mice with or without doxorubicin treatment and mice with Top2b deletion in the cardiomyocytes with or without doxorubicin treatment. Mice were treated with doxorubicin (25mg/kg, i.p.) or PBS (drug vehicle) for 16 hr or 72 hr. The heart was removed and cardiomyocytes were isolated by using a Langendorff apparatus. After purification, total RNA was extracted from the cardiomyocytes, purified, and used for gene expression analysis. Compared with that in control cardiomyocytes or cardiomyocytes with Top2b deletion, doxorubicin caused a significant expression change in the genome of cardiomyocytes from the wildtype mice. Among the changes, multiple genes encoding mitochondrial structural protein and components of the respiratory chain complexes were down-regulated 72 hr after treatment while multiple genes in the p53 pathway were up-regulated 16 hr after treatment in the wildtype cardiomyocytes. Expression changes were examined in 2 groups of mice (wild type and conditional knockout of top2b in the cardiomyocytes) treated with doxorubicin or PBS for 16 or 72 hours
Project description:High-intensity transcription and replication supercoil DNA to levels that can impede or halt these processes. As a potent transcription amplifier and replication accelerator, the proto-oncogene MYC must somehow manage these high levels of torsional stress. By comparing gene expression with the recruitment of topoisomerases and MYC to promoters, we surmised a direct association of MYC with Topoisomerases 1 (TOP1) and 2A (TOP2A) that was confirmed in vitro and in vivo. Beyond recruiting topoisomerases, MYC directly stimulates their activities in vitro and in vivo. We identify a MYC-nucleated “topoisome” complex that unites and increases the levels of both both TOP1 and TOP2, as well as their activities at promoters and enhancers. Whether TOP2A or TOP2B is included in the topoisome, is dictated by the presence of c-MYC or MYCN, respectively. Thus, in vivo and in vitro, MYC assembles tools that simplify DNA topology and promote genome function under high output conditions.
Project description:High-intensity transcription and replication supercoil DNA to levels that can impede or halt these processes. As a potent transcription amplifier and replication accelerator, the proto-oncogene MYC must somehow manage these high levels of torsional stress. By comparing gene expression with the recruitment of topoisomerases and MYC to promoters, we surmised a direct association of MYC with Topoisomerases 1 (TOP1) and 2A (TOP2A) that was confirmed in vitro and in vivo. Beyond recruiting topoisomerases, MYC directly stimulates their activities in vitro and in vivo. We identify a MYC-nucleated “topoisome” complex that unites and increases the levels of both both TOP1 and TOP2, as well as their activities at promoters and enhancers. Whether TOP2A or TOP2B is included in the topoisome, is dictated by the presence of c-MYC or MYCN, respectively. Thus, in vivo and in vitro, MYC assembles tools that simplify DNA topology and promote genome function under high output conditions.
Project description:High-intensity transcription and replication supercoil DNA to levels that can impede or halt these processes. As a potent transcription amplifier and replication accelerator, the proto-oncogene MYC must somehow manage these high levels of torsional stress. By comparing gene expression with the recruitment of topoisomerases and MYC to promoters, we surmised a direct association of MYC with Topoisomerases 1 (TOP1) and 2A (TOP2A) that was confirmed in vitro and in vivo. Beyond recruiting topoisomerases, MYC directly stimulates their activities in vitro and in vivo. We identify a MYC-nucleated “topoisome” complex that unites and increases the levels of both both TOP1 and TOP2, as well as their activities at promoters and enhancers. Whether TOP2A or TOP2B is included in the topoisome, is dictated by the presence of c-MYC or MYCN, respectively. Thus, in vivo and in vitro, MYC assembles tools that simplify DNA topology and promote genome function under high output conditions.
Project description:During transcription, DNA supercoiling generated by the advance of RNA polymerase II (Pol II) is resolved by DNA topoisomerases, enzymes that bind chromatin and produce transient breaks to relax DNA. Recently, this idea of mere facilitators of transcription progression is changing, as topoisomerases are being assigned new functions in regulating the expression of specific genes. In fact, mammalian type II topoisomerases, both the [Symbol] (TOP2A) and [Symbol] (TOP2B) paralogs, are enriched at promoter regions, where they have been proposed to trigger transcription through the generation of DNA double-strand breaks (DSBs). However, this is difficult to reconcile with the intrinsic catalytic properties of TOP2 and the high risk of genome instability that continuous production and repair of DSBs implies. Here, we show that TOP2A enforces promoter-proximal pausing of Pol II by removing transcription-associated negative DNA supercoiling. Interestingly, this topological balance and its disruption is essential for the transcriptional control of Immediate Early Genes (IEGs) and their typical bursting behaviour in response to stimulus. We therefore uncover a novel layer of transcriptional regulation that relies on canonical functions of TOP2A that are independent of aberrant DSB formation, providing a topological framework for the control of promoter-proximal pausing and the tight regulation of IEGs.
Project description:During transcription, DNA supercoiling generated by the advance of RNA polymerase II (Pol II) is resolved by DNA topoisomerases, enzymes that bind chromatin and produce transient breaks to relax DNA. Recently, this idea of mere facilitators of transcription progression is changing, as topoisomerases are being assigned new functions in regulating the expression of specific genes. In fact, mammalian type II topoisomerases, both the [Symbol] (TOP2A) and [Symbol] (TOP2B) paralogs, are enriched at promoter regions, where they have been proposed to trigger transcription through the generation of DNA double-strand breaks (DSBs). However, this is difficult to reconcile with the intrinsic catalytic properties of TOP2 and the high risk of genome instability that continuous production and repair of DSBs implies. Here, we show that TOP2A enforces promoter-proximal pausing of Pol II by removing transcription-associated negative DNA supercoiling. Interestingly, this topological balance and its disruption is essential for the transcriptional control of Immediate Early Genes (IEGs) and their typical bursting behaviour in response to stimulus. We therefore uncover a novel layer of transcriptional regulation that relies on canonical functions of TOP2A that are independent of aberrant DSB formation, providing a topological framework for the control of promoter-proximal pausing and the tight regulation of IEGs.
Project description:The 2-OG-Fe(II) dioxygenase family are critical for cellular adaptation to changes in oxygen concentration. We found that cells with OGFOD1 gene silencing in this family showed resistance to cell death under ischemia, and cDNA microarray analysis of OGFOD1 knockout human cells revealed downregulation of ATPAF1. Although reintroduction of the OGFOD1 wild-type gene to OGFOD1 KO cells restored ATPAF1 mRNA levels, the catalytically inactive OGFOD1 mutant did not. wild-type vs. OGFOD1 knock-out cells
Project description:The 2-OG-Fe(II) dioxygenase family are critical for cellular adaptation to changes in oxygen concentration. We found that cells with OGFOD1 gene silencing in this family showed resistance to cell death under ischemia, and cDNA microarray analysis of OGFOD1 knockout human cells revealed downregulation of ATPAF1. Although reintroduction of the OGFOD1 wild-type gene to OGFOD1 KO cells restored ATPAF1 mRNA levels, the catalytically inactive OGFOD1 mutant did not.