Authors:
Fernando J. López-Díaz, Philippe Gascard, Sri Kripa Balakrishnan, Jianxin Zhao, Sonia V. del Rincon, Charles Spruck, Thea D. Tlsty, & Beverly M. Emerson
Summary:
Cellular stress results in profound changes in RNA and protein synthesis. How cells integrate this intrinsic, p53-centered program with extracellular signals is largely unknown. We demonstrate that TGF-β1 signaling interferes with the stress response through coordinate transcriptional and translational repression of p53 levels, which reduces p53-activated transcription, and apoptosis in precancerous cells. Mechanistically, E2F-4 binds constitutively to the TP53 gene and induces transcription. TGF-β1-activated Smads are recruited to a composite Smad/E2F-4 element by an E2F-4/p107 complex that switches to a Smad corepressor, which represses TP53 transcription. TGF-β1 also causes dissociation of ribosomal protein RPL26 and elongation factor eEF1A from p53 mRNA, thereby reducing p53 mRNA association with polyribosomes and p53 translation. TGF-β1 signaling is dominant over stress-induced transcription and translation of p53 and prevents stress-imposed downregulation of Smad proteins. Thus, crosstalk between the TGF-β and p53 pathways defines a major node of regulation in the cellular stress response, enhancing drug resistance.
Source:
Molecular Cell; Vol. 50, Issue 4, 552-564 (05/23/13)