Post-prenylation processing meets the p53 family

GIRARDINI, JAVIER; BORINI ETICHETTI, CARLA M.; DI BENEDETTO CAROLINA

Buenos Aires

Workshop; 1st DNA Repair Network meeting; 2017

IBioBA

Most human cancers inactivate the tumor suppressor p53 through missense mutations, leading to the abundant expression of full-length point mutant proteins. p53 mutants not only lose the tumor suppressor function but may also acquire novel activities that promote tumor progression. Despite evidences showing that mutant p53 enhances tumor aggressiveness, the mechanisms underlying this activity are still poorly understood. Even if the mutation abrogates the ability to act as a transcription factor, point mutants alter gene expression through mechanisms that are not well characterized. In order to characterize those mechanisms we studied the effects of mutant p53 on gene expression. Basing on data from microarray analysis on MDA-MB-231 Triple Negative Breast Cancer cells we selected candidate genes and we confirmed the effect of mutant p53 in qRT-PCR assays. We focused on ICMT, which regulates subcellular localization and function of proteins with a C-terminal CaaX motif, including members of the RHO family, by catalyzing post-prenilation carboximethylation. To characterize the effect of p53 family members on transcription we generated reporters containing the ICMT promoter. We found that ICMT expression is regulated by complex interactions between p53 family members. We extended the characterization by deletion mapping and chromatin chIP. Our results also showed that ICMT enhances human tumor cell clonogenic potential in vitro and tumor formation in vivo in nude mice. By using three dimensional cultures we found that ICMT is able to disrupt epithelial architecture, suggesting a role in the acquisition of aggressive traits. The analysis of public databases also supports our findings on the role of ICMT as an enhancer of tumor progression and on the link with the p53 pathway. Collectively, our data shows that ICMT deregulation cooperates with the acquisition of aggressive phenotypes and suggests that the interplay with the p53 family may affect tumor progression.