FIG. 3.

Effect of CSB disruption on mRNA synthesis rate. Cells were prelabeled with [¹⁴C]thymidine for 48 h and were then pulse labeled with [³H]uridine for 1 h. Cells were lysed and poly(A)⁺ RNA was isolated using Straight A's reagent (Novagen), as described in Materials and Methods. In addition, a fraction of each lysate was subjected to total DNA extraction. The relative transcription rate (polyadenylated mRNA) was calculated as scintillations of ³H per scintillation of ¹⁴C. P values were as follows: WT versus Ink4a/ARF^−/−, P < 0.05; CSB^−/− Ink4a/ARF^−/− versus Ink4a/ARF^−/−, P < 0.05; CSB^−/− versus WT, P > 0.05.