Figure 1.

Reactivated myotubes possess low levels of dTTP and dGTP. Myotubes were transfected with siRNAs to p21 and p27 (Mt p21p27i) or to GFP as a control (Mt CTRi) and harvested at the indicated times from the beginning of treatment (Hrs fbt). Reference samples include proliferating myoblasts (Prol Mb), myoblasts cultured in suspension to attain quiescence (Q), and formerly quiescent myoblasts reactivated by replating (rQ). The dNTP pool was extracted with 60% methanol and individual dNTPs quantitated by a DNA polymerase-based assay. The data are expressed as pmoles of deoxynucleotide per absorbance unit (AU) at 260 nm (see Materials and Methods section). The results are shown as averages±S.E.M. of the indicated numbers (n) of independent experiments