Figure 4.

Thymidine synthetic enzymes are not upregulated in reactivated myotubes. (a) Myotubes were reactivated by p21 and p27 depletion (Mt p21p27i) or (b) E1A expression (Mt Ad-E1A). The mRNA levels of several dNTP synthetic enzymes were quantitated by qPCR in myotubes treated as indicated, proliferating myoblasts, and (c) quiescent myoblasts (Q) or myoblasts reactivated after quiescence (rQ). In all cases, reactivated cells were harvested in the midst of S phase. Histograms show fold increases in comparison with proliferating myoblasts, made equal to 1 (dashed lines) (averages±S.E.M. of two independent experiments). R1, R2, and p53R2 indicate the corresponding ribonucleotide reductase subunits; DCTD, deoxycytidine monophosphate deaminase; dGK, deoxyguanosine kinase; TK1 and TK2, thymidine kinases 1 and 2; TS, thymidylate synthase