Fig. 9. Farnesyl transferase activity is required for Cenp-F degradation. (A) DNA content histograms of HeLa cells cultured in the presence or absence of FTIs following release from a G1/S block. (B) Immunofluorescence images of the cells 15 hours after release from G1/S stained to detect phospho-histone H3 (red), Cenp-F (green) and DNA (blue). In the presence of SCH 66336, Cenp-F is detectable in all the interphase nuclei. (C) Immunoblots of asynchronous or G1/S blocked HeLa cells showing that Cenp-F is present in G1/S cells only when cultured in the presence of SCH 66336. (D) HeLa cells infected with retroviruses encoding C630 or the C:S mutant stained to detect myc-tagged proteins (red), Cenp-F (green) and DNA (blue). The cells were synchronised at G1/S using a single thymidine block. The cells were then analysed immediately following release (i.e. at G1/S) or 12 hours after release (i.e. in G2). Like endogenous Cenp-F, C630 is only detectable in G2 cells, whereas the C:S mutant is also detectable in G1/S cells.