Phosphorylation of eIF4GII and 4E-BP1 in response to nocodazole treatment: A reappraisal of translation initiation during mitosis

作者：Mark J. Coldwell, Joanne L. Cowan, Markete Vlasak, Abbie Mead, Mark Willett, Lisa Perry, Simon Morley · 发表于：Cell Cycle · 年份：2013 · DOI：10.4161/cc.26588 · 被引用次数：55 · 研究领域：PI3K/AKT/mTOR signaling in cancer、Microtubule and mitosis dynamics、Polyamine Metabolism and Applications

Translation mechanisms at different stages of the cell cycle have been studied for many years, resulting in the dogma that translation rates are slowed during mitosis, with cap-independent translation mechanisms favored to give expression of key regulatory proteins. However, such cell culture studies involve synchronization using harsh methods, which may in themselves stress cells and affect protein synthesis rates. One such commonly used chemical is the microtubule de-polymerization agent, nocodazole, which arrests cells in mitosis and has been used to demonstrate that translation rates are strongly reduced (down to 30% of that of asynchronous cells). Using synchronized HeLa cells released from a double thymidine block (G 1/S boundary) or the Cdk1 inhibitor, RO3306 (G 2/M boundary), we have systematically re-addressed this dogma. Using FACS analysis and pulse labeling of proteins with labeled methionine, we now show that translation rates do not slow as cells enter mitosis. This study is complemented by studies employing confocal microscopy, which show enrichment of translation initiation factors at the microtubule organizing centers, mitotic spindle, and midbody structure during the final steps of cytokinesis, suggesting that translation is maintained during mitosis. Furthermore, we show that inhibition of translation in response to extended times of exposure to nocodazole reflects increased eIF2α phosphorylation, disaggregation of polysomes, and hyperphosphorylation of sel...