Figure 5.

The effect of transient overexpression of SF2/ASF on tat pre-mRNA splicing. COS cells were transfected with the pgTAT plasmid in the presence and absence of expression vectors encoding Rev and SF2/ASF (23). Total cellular RNA was prepared 48 hr after transfection and analyzed by RT-PCR with primers specific for the first and second coding exons of tat. In the absence of Rev, the pre-mRNA undergoes complete splicing, which produces a two-exon form of tat RNA that is amplified as a 258-bp RT-PCR product (lane 1). Rev supplied in trans results in the appearance of the unspliced tat pre-mRNA, which is amplified as a 2588-bp RT-PCR product (lane 2). The unspliced pre-mRNA diminished as increasing amounts of the SF2/ASF expression plasmid were transfected (lanes 3–5).