Gene expression of protein phosphatases in rat ascites hepatoma cell lines

Gene expression of protein phosphatases 1 alpha, 1 gamma 1, 2A alpha, and 2C alpha in 14 rat ascites hepatoma cell lines was studied by Northern blot hybridization. The expression of PP1 alpha and PP2C alpha was increased and decreased, respectively, in all of the ascites hepatoma (AH) cells compared to rat liver, whereas the expression of PP1 gamma 1 and PP2A alpha was increased in about 50% of them. Relative gene expression was affected by several factors, such as harvest time, transplantation rate, percentage of free cells, and sex; the first factor was more important than the others. Relative gene expression of PP1 alpha had a negative correlation with harvest time, whereas gene expression of PP1 gamma 1 and PP2A alpha had a nonlinear (hyperbolic) correlation with harvest time. We suggest that there is a relationship between growth rate and expression of protein phosphatase genes. Our data also suggest that PP1 gamma 1 mRNA is positively controlled by PP2A alpha mRNA.