J Cancer 2018; 9(1):108-116. doi:10.7150/jca.21925 This issue
OncoSeek Limited, Hong Kong Science and Technology Parks, Hong Kong Special Administrative Region
The gene transactivation function of nuclear EGFR (nEGFR) has been studied by investigating the genomic co-occupancies of nEGFR and RNA Polymerase II (RNAPII). However, due to RNAPII pausing, the co-recruitment of RNAPII and nEGFR does not necessarily represent productive transactivation. In this study, we integrated gatekeepers of productive transcriptional elongation such as Integrator and Super Elongation Complex (SEC) to interrogate the function of nEGFR. By analyzing publicly available ChIP-seq and RNA-seq data, we aims to 1) explore the function of nEGFR, 2) unravel nEGFR target genes, and 3) discuss potential mechanisms of nEGFR chromatin recruitment. EGF treatment in HeLa cells instigated chromatin recruitment of nEGFR, ERK, RNAPII, Integrator, and SEC in a cluster of 61 EGF-responsive genes. The function of nEGFR was identified as gene-activating rather than gene-repressing. Within the cluster of EGF-responsive genes, nEGFR targeted eleven Immediate Early Genes (IEGs) — JUN, EGR1, JUNB, IER2, KLF2, FOS, FOSL1, RHOB, CCNL1, DUSP2, and DUSP5, which up-regulated >2-fold after EGF stimulation. The promoter of these target genes commonly harbors AT-rich minimal consensus sequences for nEGFR binding. In addition, TCGA data analysis demonstrated positive correlations between EGFR and JUN/FOSL1/RHOB expressions, as well as clinical correlations in specific cancer types. To our knowledge, this is the first study to compare the genome-wide distribution of nEGFR versus Integrator and SEC, providing novel insight into supporting the gene-activating function of nEGFR. We revealed a panel of eleven nEGFR target genes, which concurrently recruited nEGFR, RNAPII, Integrator, and SEC for productive transcriptional elongation.
Keywords: nEGFR, RNAPII, integrator, SEC, transcriptional elongation, gene activation