Three mRNA populations differing in turnover and processing in mouse liver.

Using kinetics of approach to steady state labeling, we have found that liver poly(A)+ mRNAs fall into three populations, differing in stability and probably in processing, as reflected in their dissimilar delays in reaching polyribosomes and turnover times. There are mRNA-1 (delay 10 min, half-life 1 hr); mRNA-2(delay 3 hr, half-life 2 hr); and mRNA-3 (delay 40 min, half-life 2.6 hr). The first two species function on free polyribosomes while the third one is operating on bound polyribosomes. The populations listed contribute 10,20 and 70%, respectively, to the total steady state labeled poly (A)+ mRNAs.