O-GlcNAcylation of core components of the translation initiation machinery regulates protein synthesis

Abstract

Protein synthesis is essential for cell growth, proliferation, and survival. Protein synthesis is a tightly regulated process that involves multiple mechanisms. Deregulation of protein synthesis is considered as a key factor in the development and progression of a number of diseases, such as cancer. Here we show that the dynamic modification of proteins by O-linked β-N-acetyl-glucosamine (O-GlcNAcylation) regulates translation initiation by modifying core initiation factors eIF4A and eIF4G, respectively. Mechanistically, site-specific O-GlcNAcylation of eIF4A on Ser322/323 disrupts the formation of the translation initiation complex by perturbing its interaction with eIF4G. In addition, O-GlcNAcylation inhibits the duplex unwinding activity of eIF4A, leading to impaired protein synthesis, and decreased cell proliferation. In contrast, site-specific O-GlcNAcylation of eIF4G on Ser61 promotes its interaction with poly(A)-binding protein (PABP) and poly(A) mRNA. Depletion of eIF4G O-GlcNAcylation results in inhibition of protein synthesis, cell proliferation, and soft agar colony formation. The differential glycosylation of eIF4A and eIF4G appears to be regulated in the initiation complex to fine-tune protein synthesis. Our study thus expands the current understanding of protein synthesis, and adds another dimension of complexity to translational control of cellular proteins.protein synthesis | translation initiation | glycosylation

Mammalian Cell Proliferation Requires Noncatalytic Functions of O-GlcNAc Transferase

“…By quantifying how much each OGT activity impacts the abundance of each protein in the cell, we have identified the biological pathways most affected by each OGT activity. Consistent with known roles for O-GlcNAc, we found that Ser/Thr glycosylation broadly regulates metabolism and gene expression, with enriched pathways including splicing (44), translation (69)(70)(71), and autophagy (72)(73)(74). Among the pathways linked to OGT's noncatalytic activities are oxidative phosphorylation, the electron transport chain, and components of the actin cytoskeleton, consistent with prior data suggesting OGT binds to the actin-regulating Ecadherin/beta-catenin complex (39).…”

O-GlcNAc regulates gene expression by controlling detained intron splicing

“…For example, O-GlcNAc modifications have been shown previously to regulate the cell cycle and play a crucial role in PI3K-Akt signaling, and both of these pathways were enriched (51). Ribosomal components were also enriched and several studies have reported a link between O-GlcNAc and ribosome biogenesis and function (52-54). However, the top two enriched pathways, the spliceosome and HSV infection, have received little to no attention as pathways regulated by OGT.…”

A cyclin-dependent kinase, CDK11/p58, represses cap-dependent translation during mitosis

“…Translation initiation factors are related to cell proliferation and tumorigenesis. For example, activation of eIF4F complex is involved in tumorigenesis [42,43], and glycosylation of eIF4G promotes cell proliferation [44]. Alterations in eIF3 subunit expression have been reported for many types of cancer cells, such as the overexpression of eIF3A, B, C, H, I, and M, and under-expression of eIF3E and F [45].…”