CircRNA inhibits DNA damage repair by interacting with host gene
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RESEARCH
Open Access
CircRNA inhibits DNA damage repair by interacting with host gene Xiaolong Xu1†, Jingwei Zhang2†, Yihao Tian1†, Yang Gao1†, Xin Dong1, Wenbo Chen1, Xiaoning Yuan1, Weinan Yin1, Jinjing Xu2, Ke Chen3*, Chunjiang He1,4* and Lei Wei1,5*
Abstract Background: Deregulated circular RNAs (circRNAs) are associated with the development of cancer and therapy resistance. However, functional research of circRNAs mostly focus on potential miRNA or protein binding and more potential regulation of circRNA on host gene DNA in cancers are yet to be inspected. Method: We performed total RNA sequencing on clinical breast cancer samples and identified the expression patterns of circRNAs and corresponding host genes in patient blood, tumor and adjacent normal tissues. qPCR, northern blot and in situ hybridization were used to validate the dysregulation of circRNA circSMARCA5. A series of procedures including R-loop dot-blotting, DNA-RNA immunoprecipitation and mass spectrum, etc. were conducted to explore the regulation of circSMARCA5 on the transcription of exon 15 of SMARCA5. Moreover, immunofluorescence and in vivo experiments were executed to investigate the overexpression of circSMARCA5 with drug sensitivities. Results: We found that circRNAs has average higher expression over its host linear genes in peripheral blood. Compared to adjacent normal tissues, circSMARCA5 is decreased in breast cancer tissues, contrary to host gene SMARCA5. The enforced expression of circSMARCA5 induced drug sensitivity of breast cancer cell lines in vitro and in vivo. Furthermore, we demonstrated that circSMARCA5 can bind to its parent gene locus, forming an R-loop, which results in transcriptional pausing at exon 15 of SMARCA5. CircSMARCA5 expression resulted in the downregulation of SMARCA5 and the production of a truncated nonfunctional protein, and the overexpression of circSMARCA5 was sufficient to improve sensitivity to cytotoxic drugs. Conclusion: Our results revealed a new regulatory mechanism for circRNA on its host gene and provided evidence that circSMARCA5 may serve as a therapeutic target for drug-resistant breast cancer patients. Keywords: Breast cancer, circRNA, DNA damage repair, R-loop, Host gene
* Correspondence: [email protected]; [email protected]; [email protected] † Xiaolong Xu, Jingwei Zhang, Yihao Tian and Yang Gao contributed equally to this work. 3 Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China 1 School of Basic Medical Sciences, Wuhan University, Wuhan 430071, Hubei, China Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. T
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