Figure 7.

The 3′UTRs of IL-2 and IL-6 destabilize the fGH mRNA in the presence and absence of the calcium ionophore A23187. The entire 3′UTR of IL-2 or IL-6 was inserted near the termination codon of the fGH gene, generating fGH-IL2 and fGH-IL6, respectively. RNA was isolated at various times after serum stimulation of NIH 3T3 cells stably transfected with either gene and quantitated by RNase protection assay. The data shown are means ± SEM from two experiments. Addition of A23187 at the time of serum stimulation resulted in only a modest increase in the survival of the mRNAs compared with the effect on mRNAs containing only A+U-rich insertions (see Fig. 2).