EIF4EBP1 and lung carcinoma: By mutating these two sites and showing that the S5A/S6A 4E-BP1 mutant protein no longer supports the hyper-O-GlcNAcylation-induced downregulation of OGT protein level like the wild-type 4E-BP1 protein does, we provide evidence supporting a scenario in which the O-GlcNAcylation of proteins regulating translation may represent one key mechanism in mediating the compensatory modulation of OGT expression for maintaining O-GlcNAc homeostasis in lung cancer cells.