Fig. 5. Inhibition of cell proliferation by p27wt and p27R90G. RAT1 cells were infected with recombinant retroviruses expressing either p27wt or p27R90G. (A) The rate of cell proliferation of resistant cell pools relative to a pool of cells infected with a control (pbabe-puro) virus. (B) Average doubling time calculated from logarithmic plots of two independent infections. (C) Western blots documenting the expression of the proteins indicated and the amounts of cyclin A/p27 and cyclin E/p27 in exponentially growing cells infected with the viruses indicated.