Fig. 5. Quantification of mRNA for - and ß-tubulin. Total RNA was isolated and hybridized to ³²P-labeled antisense probes to -tubulin or ß-tubulin. A second antisense riboprobe to the gene encoding glyceraldehyde-phosphate dehydrogenase (GAPDH) was included in each reaction as an internal control. Following nuclease digestion, the products were separated on a polyacrylamide gel and the protected fragments were identified and quantified on a Storm phosphoimager. The results were also verified by liquid scintillation counting of bands excised from the gel. Relative amounts of tubulin message were calculated by dividing the radioactivity in the tubulin band by the radioactivity in the GAPDH band, and then expressing the results relative to WT cells set at 100%.