Competence of soluble cell extracts as microtubule assembly systems. Comparison of simian virus 40 transformed and nontransformed mouse 3T3 fibroblasts.

Soluble cell extracts from simian virus 40 transformed mouse 3T3 fibroblast cells (SV101) and nontransformed mouse BALB/c-3T3 cells were compared as microtubule assembly systems. Extracts from the transformant were found to be at least as competent for microtubule assembly under standard conditions as those from normal cells. This observation proves that the defects in cytoplasmic microtubule skeletons reported in the literature for various transformed cell lines are not due to the loss of integrity of the tubulin molecule itself, but rather to transformation-dependent changes in the regulatory mechanisms controlling in vivo microtubule assembly.