Fig. 4. Retention of intron sequences in the perlecan transcript in hamster tsTM18 cells. Total RNA and genomic DNA of CHO-K1 and tsTM18 cells were treated with or without DNase and then analysed with primer pair f6/r2 by RT-PCR for RNA or by PCR for DNA. (A) After treatment with DNase, a 97-bp product appears in RNA fraction, and a 300-bp product is present in RNA from tsTM18 cells cultured at 39°C. No PCR products were obtained with DNA as template. The closed triangle indicates a transcript with retained intron sequences, and the open triangle indicates the transcript predicted from the sequence. (B) Result of RT-PCR with primer pair f2/r2. Lane numbers correspond to those in panel A. Splice variants are seen in the amplification products of tsTM18 cells incubated at 39°C (lane 5). (C) Results of RT-PCR and PCR without DNase pretreatment. Triangles indicate the product predicted from the sequence. A 300-bp PCR product was amplified from DNA.