FIG. 3.

Tid-1 is upregulated at both RNA and protein levels upon cellular senescence. (A) Tid1 RNA levels were analyzed by RT-PCR in young (P2) and senescent (P7 or P4) MEFs and REFs using sets of primers that discriminate between the long and short isoforms. (B and C) Tid-1 proteins accumulate in primary MEFs and REFs upon serial passaging and in REF52 cells upon premature senescence triggered by activated ras. Western blots were probed with the Tid1-specific monoclonal antibody PAb RS13 or the Tid1S specific polyclonal antibody PAb S9. Equal loading was confirmed with a monoclonal antiactin antibody.