A large fraction of cyclin D3 bound the nuclear matrix. (A) Rag2^−/− pro–B cells were cultured in IL-7 with LY294002 and CHX for the times indicated. TCLs were SDS-extracted (5 × 10⁵ cells per sample), resolved by SDS-PAGE, and membranes were probed for cyclin D3, cyclin D2, and Actin. Summary of three experiments, where cyclin expression was normalized to Actin, standardized as a ratio of the treated sample relative to the expression level in untreated samples (arbitrary units, A.U.) and reported graphically as the mean ± SD. (B and C) Rag2^−/− pro–B cells (B) or MEFs (C) were cultured with or without the inhibitors LY294002 and CHX for 75 min. Cell aliquots were subjected to subcellular fractionation. Fractions were resolved by SDS-PAGE and membranes probed for cyclin D3 and fraction-specific controls α-tubulin (soluble), Histone H3 (chromatin), and Lamin A/C (nuclear matrix). Relative molecular mass (kD) is as indicated. Data are representative of three independent experiments.