Characterization of mutant p53-based oncogenic mechanism: regulation of CPSF6

CARLA BORINI; CAROLINA ROSSI; SOLANGE IBARRA; JAVIER E. GIRARDINI

VALPARAISO

Congreso; Third Meeting of the Latin American Zebrafish Network (LAZEN); 2014

P53 point mutants, besides losing the tumor suppressor function of the wt protein, may acquire novel activities that promote the development of aggressive and metastatic tumors. We have previously found that the prolil-isomerase Pin1 cooperates with mutant p53 to alter gene expression in breast cancer cells. In particular, both proteins induce the expression of 10 genes (Pin1/mutant p53 signature) whose expression is associated with the development of aggressive breast tumors. Among them we found CPSF6, which codes for a 68 kDa protein, belonging to the CFIm processing factor that regulates mRNA polyadenilation. Even if several aspects CFIm function in polyadenilation were described, little is known regarding how CPSF6 may be involved in human cancer. In order to understand the mechanisms underlying the pro-oncogenic role of CPSF6, we studied the consequences of overexpression of zebrafish Cpsf6 (DrCpsf6) during embryogenesis in zebrafish. We cloned the sequence of DrCpsf6 and we observed a nuclear localization reminiscent of paraspeckles upon ectopic expression. Surprisingly, we found that upon microinjection in zebrafish embryos, Cpsf6 expression is readily detectable at early stages but becomes almost completely absent at later stages, suggesting the existence of robust posttranslational regulatory mechanisms. Further studies showed that oncogenic signals do not alter subcellular localization but may be involved in protein stability.