FIGURE 4.
Rb represses the transcription of CSIG but does not affect the transcription of ARF or p27KIP1 during senescence. A, growing (G) and Ras-senescent (S) 2BS cells were processed for ChIP using an antibody against Rb, p107, or p130 or using nuclear extract (input) or IgG as a negative control. DNA fragments were amplified by PCR from the promoter regions of CSIG, PCNA, CCNA2, ARF, p27, and β-actin. B, the 2BS cells expressing vector alone (Ctrl) or H-Ras (pWZL-Ras-Hygro) with the indicated combination of vector, shRNA against Rb (shRb), p107 (shp107), and p130 (shp130) were analyzed for the indicated proteins. C, the cell populations described in B were assessed for BrdU incorporation and SAHF formation. The values represent the means and standard errors for the three independent experiments. D, the 2BS cells expressing a combination of Ras and the vector (Ctrl), E1A, or E1AΔN were analyzed for the indicated proteins. E, the cell populations described in D were assessed for BrdU incorporation and SAHF formation. The values represent the means and standard errors from three independent experiments. Ctrl, control.