FIG. 3.

Senescence-associated CENP-A reduction is mediated not only by transcriptional control but also by posttranslational proteolysis. (A) Northern blotting of the senescent and the quiescent TIG3 cells. The transcript levels of CENP-A, H2B, and GAPDH are shown. GAPDH and methylene blue staining were used as loading controls. PDLs and the time points after infection or treatment are indicated at the top. (B) Immunoblotting of the senescent and the quiescent cells. TCE (2 × 10⁴ cells) were resolved by SDS-PAGE, followed by immunoblotting with the indicated antibodies. (C) The protein levels of CENP-A and cyclin A were determined in TCE prepared from cells treated with 50 μg of cycloheximide/ml for the indicated time points (left panel). The integrated density at 0 h was set at 100%. The half-lives of CENP-A and cyclin A were estimated by the band density as described in Materials and Methods. Growth curve of the drug-treated cells (right panel). The number of cells at 0 h was set at 100%.