the present analysis of regulation of tk mrna in balb/c 3t3 cells showed that ( i ) the increase in tk activity depended on the availability of tk mrna , ( ii ) the level of tk mrna between g0 and s increased more than 20-fold , ( iii ) the rate of run-on tk transcription increased at most 2- to 4-fold between the g0 and s phases , ( iv ) the half-life of tk mrna was greater than 8 to 12 h in the s and m phases and decreased as cells entered quiescence , ( v ) the tk mrna increase was fully blocked by inhibition of protein synthesis by only 60 % , ( vi ) this inhibition was completely effective for up to about 10 h following serum addition and progressively much less effective when the drugs were added later .
C0007591
m phases
C0007634
cells