FIG. 4.

70–71Ter within exon 2 fails to mediate a reduction in mRNA abundance in the absence of introns 3 through 6 unless intron 2, the new 3′-most intron, is moved from residing 24 bp downstream of the nonsense codon to residing 70 bp downstream of the nonsense codon. NIH 3T3 cell transfections and the purification and analysis of total-cell RNA were as described in the legend to Fig. 1. Values shown are an average of the values obtained from two independently performed experiments, which did not differ by more than 8%.