FIG. 3.

RT-PCR analysis of APRT and HPRT mRNA. (A) Total RNA was extracted from CHO cell lines carrying a deletion of the APRT gene, the wild-type (wt) APRT, and APRT genes with insertions of CAG repeats. (B) Total RNA was extracted from CHO cells transiently transfected with the control plasmid, a plasmid containing the intact human HPRT minigene, and a set of plasmids containing CAG repeat tracts of various lengths cloned into the intron of the HPRT minigene. Junctions between exons 2 and 3 of the hamster APRT gene and junctions between exons 2 and 3 of the human HPRT minigene were amplified by RT-PCR and were separated on agarose gels. The lower band in each lane corresponds to the product expected for correct splicing of exons 2 and 3. Upper bands correspond to transcripts containing the CAG exon incorporated between exons 2 and 3. MW, molecular weight.