Incorporation of [³⁵S]methionine into cyclin D1 was decreased by exposure to SAHA. (A) Jeko 1 cells were metabolically labeled in the absence of SAHA for 2 hours, followed by an additional 3 hours of metabolic labeling of the cells either with or without SAHA. At each time point, cells were collected and lysed, and cyclin D1 protein was immunoprecipitated and fractionated in a SDS-PA gel. Signal of cyclin D1 protein was detected on X-ray film (left); intensity of the bands were quantified and graphically plotted. (right). (B) To measure the immunoprecipitated cyclin D1 protein and the mRNA levels, the same experiment was performed in the absence of radioisotope; the proteins and mRNA were extracted after a 3-hour culture either with or without SAHA (5 μM) and analyzed by Western and Northern blot analysis.