FIG. 5.

Accumulation of spliced gas5 RNA in (a) translation-inhibited or (b) growth-arrested cells. Northern analysis, using probes for gas5 and UHG spliced transcripts as well as U75 snoRNA, β-actin, and rpS16 mRNAs, was performed on total RNA isolated from NIH 3T3 cells treated with 20 μg of cycloheximide/ml (lanes 1 to 5), 280 ng of pactamycin/ml (lanes 6 to 10) or 20 ng of rapamycin/ml (lanes 11 to 15) for 0 (untreated), 1, 2, 5, and 12 h (a) or growth arrested by either contact inhibition (lanes 1 to 5) or serum starvation (lanes 6 to 10) for 0 (growing), 12, 24, 36, and 48 h (b). For each timecourse, equal amounts of RNA were loaded in the lanes (the internal controls show that lane 8 in panel a was underloaded). The progressive increase in mobility of the gas5 and UHG transcripts upon cycloheximide and pactamycin treatment may reflect poly(A) tail shortening.