The RAX/PACT-PKR Stress Response Pathway Promotes P53 Sumoylation and Activation, Leading to G₁ Arrest
Overview
Affiliations
Cellular stresses, including growth factor deprivation, inflammatory cytokines or viral infection promote RAX/PACT-dependent activation of the double-stranded RNA-dependent protein kinase, PKR, to phosphorylate eIF2α, resulting in translation inhibition and apoptosis. In addition, PKR has been reported to regulate p53, STAT1 and NFκB. Here, we report that RAX/PACT interacts with the SUMO E2 ligase Ubc9 to stimulate p53-Ubc9 association and reversible p53 sumoylation on lysine 386. In addition, expression of RAX/PACT in a variety of cell lines promotes p53 stability and activity to increase p53 target gene expression. Significantly, while the expression of RAX/PACT, PKR or p53 alone has little effect on the cell cycle of p53-null H1299 cells, co-expression of p53 with either RAX/PACT or PKR promotes a 25-35% increase of cells in G₁. In contrast, co-expression of RAX/PACT with the sumoylation-deficient p53(K386R) mutant or with the desumoylase SENP1 fails to induce such a G₁ arrest. Furthermore, co-expression of p53, RAX/PACT and the dominantnegative PKR(K296R) mutant inhibits RAX/PACT-induced, p53-dependent G₁ growth arrest and expression of RAX/PACT in pkr(+/+) but not pkr(-/-) MEF cells promotes p53 and p21 expression following gamma irradiation. Significantly, p53 stability is decreased in cells with reduced RAX/PACT or PKR following doxorubicin treatment, and expression of exogenous RAX/ PACT promotes phosphorylation of wild-type but not p53(K386R) on serine 392. Collectively, results indicate that, in response to stress, the RAX/PACT-PKR signaling pathway may inhibit p53 protein turnover by a sumoylation-dependent mechanism with promotion of p53 phosphorylation and translational activation leading to G₁ cell cycle arrest.
Luteolin protects DYT- cells from apoptosis by suppressing PKR activation.
Frederick K, Patel R Front Pharmacol. 2023; 14:1118725.
PMID: 36874028 PMC: 9974672. DOI: 10.3389/fphar.2023.1118725.
PACT promotes the metastasis of basal-like breast cancer through Rac1 SUMOylation and activation.
Wei L, Wang W, Yao J, Cui Z, Xu Z, Ding H Oncogene. 2022; 41(37):4282-4294.
PMID: 35974143 DOI: 10.1038/s41388-022-02431-6.
Yang L, Lin K, Zhu L, Wang H, Teng S, Huang L Commun Biol. 2022; 5(1):822.
PMID: 35970927 PMC: 9378715. DOI: 10.1038/s42003-022-03778-y.
Cell Death and the p53 Enigma During Mammalian Embryonic Development.
Raj S, Jaiswal S, DePamphilis M Stem Cells. 2022; 40(3):227-238.
PMID: 35304609 PMC: 9199838. DOI: 10.1093/stmcls/sxac003.
Lu Y, Yang Y, Hu T, Duan W Transl Cancer Res. 2022; 10(2):806-816.
PMID: 35116411 PMC: 8799081. DOI: 10.21037/tcr-20-2531.