Relative quantitative RT-PCR of CSB transcripts isolated from UV61/pc3.1-CSBwt and UV61/pc3.1-CSBE646Q. CSB expression in hamster transfectant cell lines was determined relative to the internal 18S rRNA standard as described in MATERIALS AND METHODS. RT-PCR products were electrophoresed on an 8 M urea-6% polyacrylamide gel. The RT-PCR products from the CSB mRNA and the 18S rRNA using site-specific CSB and 18S primers respectively are indicated. Reaction products from RT-PCR amplifications are as follows: lanes 1–3, UV61/pc3.1-CSBwt using CSB primers (lane 1), CSB primers plus 18S RNA primers (lane 2), and 18S RNA primers (lane 3); lanes 4–6, UV61/pc3.1-CSBE646Q using CSB primers (lane 4), CSB primers plus 18S RNA primers (lane 5), and 18S RNA primers (lane 6).