Cloning and expression of the human p8, a nuclear protein with mitogenic activity

We have previously identified a new rat mRNA, provisionally named p8, which showed a strong, but transient, induction in the pancreas in response to a cute pancreatitis. We report hen the cloning and sequencing of the human p8 cDNA. The human p8 polypeptide is 82 aminoacids long and shows an overall identity of 74% with the rat counterpart. The complete structure of the p8 gene was also established. The p8 gene comprises three exons separated by t wo introns and the gene was mapped to chromosome 16. Analysis of the p8 pri mary structure suggested the presence of a bipartite motif of nuclear targe ting, indicating that p8 may function within the nucleus. This presumption has been confirmed by transfection of COS-7 cells with the p8 cDNA followed by immunostaining with specific antibodies. p8 mRNA expression is induced in some, but not all, cells by serum starvation and ceramide. To analyze th e ps function, we stably transfected HeLa cells with a p8 expression plasmi d, and measured their growth and their sensitivity to apoptosis. Response t o TNF alpha and staurosporine-induced apoptosis was not modified by p8 expr ession. However, cells expressing p8 grew significantly more rapidly.