Nelfe Modulates Chromatin Accessibility To Amplify The Transcription Of Myc-Associated Genes In Hepatocellular Carcinoma

Global transcriptomic alterations are often observed in cancers, including hepatocellular carcinoma (HCC). How these large changes are modulated remain elusive. We have previously demonstrated that the overexpression of Negative elongation factor E (NELFE) contributes to the transcriptomic imbalance in HCC through MYC signaling, which regulates more than 15% of the genome. However, how NELFE modulates MYC to enhance the transcription of pro-oncogenic mRNAs is unknown. It is known that the status of the chromatin is essential for gene expression. Previous studies have shown that NELF-mediated stalling of Pol II can enhance gene expression by blocking promoter-proximal nucleosome assembly in Drosophila. Here, we propose that NELFE modulates the status of the chromatin to regulate gene expression to promote hepatocarcinogenesis. Accordingly, the overexpression of NELFE and MYC in the h-TERT immortalized hepatocyte cells, HHT4, significantly enhanced cancer associated phontypes, including proliferation and colony and spheroid formation. NELFE and MYC ChIP-PCR demonstrated that both NELFE and MYC co-occupy the promoter regions of two proliferative genes, cyclin E2 and PA2G4. Furthermore, the signals of MYC and H3K27ac, a histone marker associated with open and active promoter and enhancer elements, were decreased in these regions by NELFE-depletion. These results provide a possible mechanism whereby NELFE plays an essential role in modulating the status of the chromatin to regulate MYC-induced gene expression. Current studies include the use of CRISPR/Cas9 tools to generate NELFE mutants and ATAC-seq and ChIP-seq (MYC and NELFE) to explore NELFE9s role in chromatin modulation genome-wide. These assays will allow us to determine the dynamic function and pro-oncogenic roles of NELFE and their effect on the MYC targets, including cyclin E2 and PA2G4 transcripts. Key words: NELFE, chromatin, transcription, HCC, liver, MYC. Citation Format: Kai Zhang, Hien Dang, Anna Barry. NELFE modulates chromatin accessibility to amplify the transcription of MYC-associated genes in hepatocellular carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2483.