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Abstract 5249: The transcriptional regulation of CCND1 by miR-15a-5p in the nucleus of colorectal carcinoma cell lines

Although miRNAs are important post-transcriptional regulators of gene expression in cytoplasm, more and more evidences demonstrate that miRNAs also have nuclear functions. The majority of miRNAs are present in both the cytoplasm and the nucleus. The canonical function of translational repression in cytoplasm is well studied, but the functions of nuclear miRNAs are currently not well understood. From previous studies, we found that miR-15a-5p (miR-15a for short) can be detected in the nucleus of the colon cancer cell line. By transfected miR-15a labelled with biotin, we validated that miR-15a could bind to DNA (especially dsDNA) in the nucleus of colorectal carcinoma cell line HCT116. To find the targets of miR-15a in the nucleus, we scanned the promoter region of the potential targets which were predicted by Targetscan, miRWalk, and miRDB. The promoter of CCND1 has one region that is complementary to miR-15a. By integrating the RNA-seq data and miRNA-Seq data from NCI60 cell line panel and TCGA (The Cancer Genome Atlas), we found that CCND1 was negatively regulated by miR-15a in colorectal cancer. To confirm that miR-15a regulates CCND1’s transcription in the nucleus, we constructed the promoter of CCND1 and a luciferase reporter into one plasmid, then site-specific mutation was introduced into the potential binding site of miR-15a in the promoter of CCND1. The luciferase assay demonstrated that the mutation in the binding site decreased the expression of CCND1, which validate that miR-15a may regulate the expression of CCND1 by binding to the promoter of CCND1 in the nucleus. The next step, we will further study the function of nuclear miR-15a distinct from the canonical paradigm in carcinogenesis. Note: This abstract was not presented at the meeting. Citation Format: Zhenzhen Liu, Xue Bai, Chunyan Li. The transcriptional regulation of CCND1 by miR-15a-5p in the nucleus of colorectal carcinoma cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5249.