Gβγ subunits colocalize with RNA polymerase II and regulate transcription in cardiac fibroblasts

Gil gamma subunits mediate many different signaling processes in various compartments of the cell, including the nucleus. To gain insight into the functions of nuclear Gil gamma signaling, we investigated the functional role of Gil gamma signaling in the regu-lation of GPCR-mediated gene expression in primary rat neonatal cardiac fibroblasts. We identified a novel, negative, regulatory role for the Gil1 gamma dimer in the fibrotic response. Depletion of Gil1 led to derepression of the fibrotic response at the mRNA and protein levels under basal conditions and an enhanced fibrotic response after sustained stimulation of the angiotensin II type I receptor. Our genome-wide chromatin immunoprecipitation experiments revealed that Gil1 colo-calized and interacted with RNA polymerase II on fibrotic genes in an angiotensin II-dependent manner. Additionally, blocking transcription with inhibitors of Cdk9 prevented as-sociation of Gil gamma with transcription complexes. Together, our findings suggest that Gil1 gamma is a novel transcriptional regulator of the fibrotic response that may act to restrict fibrosis to conditions of sustained fibrotic signaling. Our work expands the role for Gil gamma signaling in cardiac fibrosis and may have broad implications for the role of nuclear Gil gamma signaling in other cell types.

Automated summary

In this study, a negative regulatory role for the Gil1 gamma dimer in the fibrotic response was identified in primary rat neonatal cardiac fibroblasts. Gil1 was found to colocalize and interact with RNA polymerase II on fibrotic genes in an angiotensin II-dependent manner. This finding expands the role of Gil gamma signaling in cardiac fibrosis and suggests its importance in other cell types.