Role of eIF3a in regulating cell cycle progression.

Translational control is an essential process in regulation of gene expression, which occurs at the initiation step performed by a number of translation initiation factor complexes. eIF3a (eIF3 p170) is the largest subunit of the eIF3 complex. eIF3a has been suggested to play roles in regulating translation of a subset of mRNAs and in regulating cell cycle progression and cell proliferation. In this study, we examined the expression profile of eIF3a in cell cycle and its role in cell cycle progression. We found that eIF3a expression oscillated with cell cycle and peaked in S phase. Reducing eIF3a expression also reduced cell proliferation rate by elongating cell cycle but did not change the cell cycle distribution. However, eIF3a appears to play an important role in cellular responses to external cell cycle modulators likely by affecting synthesis of target proteins of these modulators.