The Protein Stability and Transcriptional Activity of p63α are Regulated by SUMO-1 Conjugation

Abstract

Post-translational modification of proteins by the ubiquitin-like molecule SUMO-1 regulates their stability and activity with crucial implications for many cellular processes. Here we show that p63α, but not p63β and γ, is sumoylated in vitro and in vivo at a single lysine residue, K637, in the post-SAM domain. SUMO-1 attachment targets ∆Np63α for proteasome mediated degradation while it does not influence p63α intracellular localization, as wild-type protein and a mutant carring the K637 mutated into arginine (K637R), have the same nuclear localization. Four natural p63 mutations, falling within the SAM and post-SAM domain of p63α, were found to be altered in their sumoylation capacity. The transcriptional activities of the natural mutants and of K637R were strongly increased compared to that of wild type p63, suggesting that sumoylation has a negative effect on p63 driven transcription. The findings that ∆Np63α protein levels are regulated by SUMO-1 and that this regulation is altered in natural p63 mutants, suggest that SUMO conjugation to p63 plays a critical role in regulating the biological activity of p63.

Small Ubiquitin-like Modifier (SUMO) Modification Mediates Function of the Inhibitory Domains of Developmental Regulators FOXC1 and FOXC2

“…Mild mutations in the SC motifs of the androgen receptor, however, are associated with both prostate cancer and androgen insensitivity syndrome, 4 indicating that subtle changes in SUMOylation can have significant in vivo consequences. These effects may be particularly relevant to developmental regulators because mutations in TBX22 (53) or TP63 (54,55) that affect its SUMOylation and function are associated with craniofacial abnormalities. In addition, because enhanced SUMOylation is a specific response to cellular stressors such as heat shock and oxidative stress, some of the teratogenic effects of these stressors (56) could in part be due to alterations in the SUMOylation, and hence the function, of critical regulators such as FOXC1 or FOXC2.…”

p63 and p73 in human cancer: defining the network

“…The p73a and p63a isoforms can also be regulated by conjugation with the small ubiquitin-like modifier SUMO-1. Sumoylation was shown to modestly inhibit the transcriptional activity of p73 and p63 (Minty et al, 2000;Ghioni et al, 2005). However, the relatively small fraction of total cellular p63 and p73 found to be sumoylated may not be sufficient to significantly inhibit their overall transactivational functions (Blandino and Dobbelstein, 2004).…”

A Novel Link Between SUMO Modification and Cancer Metastasis

“…Therefore, it is tempting to speculate that the change in the expression of the deSUMOylating enzyme might possibly affect SUMOylation of proteins including reptin. 9 [39][40][41][42][43][44][45][46] however, the functional significance of SUMOylation of these molecules in cancer has not yet been extensively studied. SUMOylation has different functions in the regulation of oncogenes and tumor suppressor genes.…”