4E1RCat is an inhibitor of eIF4E:eIF4GI interaction, with an IC50 an of ∼4 μM. 4E1RCat binding to eIF4E also interferes with eIF4G and 4E-BP binding. 4E1RCat inhibits ribosome recruitment to mRNA in a cap-dependent manner. 4E1RCat blocks the capped mRNA translation, and the translation is activated by CDK1/CYCB1. Nearly all new protein synthesis in both mitosis and interphase is cap-dependent and -sensitive to 4E1RCat treatment, in HeLa and U2OS cells.