Preferential Translation of Internal Ribosome Entry Site-containing mRNAs during the Mitotic Cycle in Mammalian Cells

A cell synchronization protocol was established in which global and individual mRNA translational efficiencies could be examined. While global translational efficiency was reduced in mitotic cells, ∼3% of mRNAs remained predominantly associated with large polysomes during mitosis, as determined by cDNA microarray analyses. The 5′-non-coding regions of six mRNAs were shown to contain internal ribosome entry sites (IRES). However, not all known mRNAs that contain IRES elements were actively translated during mitosis, arguing that specific IRES sequences are differentially regulated during mitosis.