Protein synthesis and mitosis. 1. Influence of anti-tubulins on protein synthetic activity in synchronous M-phase and asynchronous populations of HeLa S-3 cells

Abstract

Asynchronous and synchronous HeLa S-3 suspension cultures treated with colcemid and vinblastine (VLB) resulted, in the former case, in suppression of 3H-leucine incorporation into protein which became increasingly apparent as the percentage of M-phase-arrested cells increased. In the latter case, where no cells were allowed to enter M-phase, no significant inhibition of incorporation occurred. M-phase cells were collected by shake-off from asynchronous monolayers, or alternatively monolayers presynchronised 10 h before shake-off, either in the presence or absence of alkaloids. In both cases, alkaloid-treated cultures showed marked inhibition of protein synthesis, while controls were largely unaffected. The results indicate that marked suppression of protein synthesis in alkaloid-arrested M-phase population is primarily due to the inability of cells to complete mitosis. Arrested cells showed no increase in size or protein content with time, but began disintegrating approximately 6-7 h after alkaloid treatment. The necessity for cells to traverse M-phase quickly is emphasised, otherwise any transient decline of protein synthesis during M-phase becomes grossly exaggerated.