Staufen1 Represses the FOXA1-Regulated Transcriptome by Destabilizing FOXA1 mRNA in Colorectal Cancer Cells
Transcription factors play key roles in development and diseases by controlling gene expression. Forkhead Box A1 (FOXA1) is a pioneer transcription factor essential for mouse development that plays important roles in prostate and breast cancer. In colorectal cancer (CRC), we have found that FOXA1 is significantly downregulated, suggesting potential tumor suppressive functions. However, the mechanism(s) by which FOXA1 is downregulated in CRC cells remain largely unclear. We investigated the regulation of FOXA1 expression in CRC, focusing on well-differentiated CRC cells where it is robustly expressed. Genome-wide stability assays identified FOXA1 as an unstable mRNA in CRC cells. We validated FOXA1 mRNA instability in multiple CRC lines and patient-derived CRC organoids and found FOXA1 mRNA is degraded via its 3'UTR. Through FOXA1 3'UTR RNA pulldowns, we identified Staufen1 (STAU1) as a potential regulator of FOXA1. Indeed, knockdown of STAU1 results in increased expression of FOXA1 mRNA and protein due to increased FOXA1 mRNA stability. A subset of the STAU1-regulated transcriptome is enriched for FOXA1 targets, whose expression also increases upon STAU1 knockdown. Collectively, this study uncovers the molecular mechanism by which FOXA1 is regulated in CRC and provides insights into our understanding of the complex mechanisms of gene regulation in cancer. Overall design: mRNA profiles from LS180 upon siCTRL, or siSTAU1 after 72 + 72 hours of transfection. mRNA profiles from LS180 and HCT116 upon 5 ug/ml Actinomycin D treatment at different time points.