PTEN-dependent regulation of genome-wide transcription during metabolic stress [RNA-Seq]
PTEN is implicated in a wide variety of pathophysiological conditions and traditionally studied in the context of the PIK3-AKT-mTOR axis. Recent studies from our group and others have reported a novel role of PTEN in the regulation of transcription at the genome-wide scale. This emerging role of PTEN on global transcriptional regulation is providing a better understanding of various diseases, including cancer. Since cancer progression is an energy-demanding process and PTEN is known to regulate metabolic processes, we sought to understand the role of PTEN in transcriptional regulation under metabolic stress, a condition often developing in the tumor microenvironment. In the present study, we demonstrate that PTEN modulates genome-wide RNA Polymerase II (Pol II) occupancy in cells undergoing glucose deprivation. The glucose-deprived PTEN null cells were found to continue global gene transcription, which may activate a survival mode. However, cells with constitutive PTEN expression slow transcription, an evolutionary mechanism that may save cellular energy and activate programmed cell death pathways, in the absence of glucose.  Interestingly, alternative exon usage by PTEN null cells is increased under metabolic stress compared to PTEN expressing cells. Overall, our study comprehensively demonstrates distinct mechanisms involved in PTEN-dependent genome-wide transcriptional control under metabolic stress. Our findings provide a new insight in understanding the tumor microenvironment and how PTEN loss of function, whether by genetic or non-genetic mechanisms, can contribute to a favorable transcriptional program employed by tumor cells to escape apoptosis, hence developing more aggressive and metastatic phenotypes. Overall design: RNA-seq was performed on BT-549 control and PTEN over-expressing BT-549_PTEN cell.