Cloning and expression of the Rb-related mouse p130 mRNA

The mouse p130 cDNA was cloned from a thymus-derived library using the human p130 cDNA as a probe. The 4515-bp mouse cDNA encodes a putative 1092 aa protein with predicted molecular mass of 123 kD. Comparison of mouse and human sequences reveals the mouse protein lacks 43 aa in a conserved domain, relative to the human sequence, located amino-terminal to the pocket region. Northern analysis of P19 embryonal carcinoma (EC) and RA-induced P19 cultures indicates p130 mRNA is not expressed at detectable levels in undifferentiated stem cells and is strongly upregulated after post-mitotic neurons begin to accumulate. Northern analysis of adult mouse tissues indicated that the 4.8 kb p130 mRNA is expressed ubiquitously, however, a putative 5'-truncated 1.7 kb isoform is detected solely in testis. Forced expression of mouse p130 induced growth suppression of P19 EC cells and Western analysis of transfected P19 cells suggested the cloned cDNA encodes the full-length p130 protein.