Abstract 1446: Super-enhancer identification via Bru/BrUV-Seq and H3K27Ac ChIP-Seq

Abstract

Abstract Transcriptional super-enhancers (SEs) are large clusters of active enhancers that drive expression of genes critical to cell identity and function. In cancer and other human diseases, SEs can be acquired through somatic aberrations. Importantly, SEs and their target genes are particularly sensitive to perturbation, making this mechanism a promising target for both diagnosis and therapy. Histone modification H3K27Ac is a good single predicative marker of active enhancers, though additional marks would help. Accordingly, a common approach to SE identification is using H3K27Ac ChIP-Seq. The non-TSS (transcription start site) histone binding sites (e.g., principally excluding TSS±2.5kb regions) are mapped to genome and then subject to near-neighbor stitching (e.g., within 12.5kb). From the resulted relatively broad regions, SEs are identified by exceptional binding enrichment. Another potentially powerful approach is to use Bru/BrUV-Seq in combination. By directional sequencing of bromouridine(Bru)-labeled nascent RNAs, Bru-Seq has been developed to study nascent transcription. In the derivative BrUV-Seq, UV irradiation is additionally conducted to stabilize transcripts prior to labeling, thereby allowing more sensitive detection of TSSs and unstable transcripts, including enhancer RNAs (eRNAs). It has been shown that eRNAs indicate enhancer activity better than H3K27Ac binding. In this study, both approaches were used to identify SEs for three colon cancer cell lines, HCT-116, SW48, and SW620. We have demonstrated that Bru/BrUV-Seq has advantages in differentiating between mRNAs and eRNAs, and between overlapping transcripts; the reduced complexity helps prevent false identifications, which inflated our results obtained from ChIP-Seq. Citation Format: Chunlao Tang, Vipin Yadav, Hui-Rong Qian, Jason B. Cunningham, Hong Gao, Yushi Liu, Jason C. Ting, Steven M. Bray, Philip J. Ebert, Yuhao Lin, Amit Aggarwal, John N. Calley, Bharvin K. Patel. Super-enhancer identification via Bru/BrUV-Seq and H3K27Ac ChIP-Seq [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1446. doi:10.1158/1538-7445.AM2017-1446