EIF4G2

EIF4G2 Full Name

eukaryotic translation initiation factor 4 gamma, 2

EIF4G2 Introduction

eIF4G2, also known as DAP-5 or p97, is a member of the eukaryotic initiation factor 4G family, yet it stands apart from its canonical counterparts. While eIF4G1 and eIF4G3 are central to cap-dependent translation, eIF4G2 functions as a non-canonical initiation factor. It lacks the N-terminal domain required for binding the cap-binding protein eIF4E, which fundamentally alters its role in protein synthesis. Structurally, it retains the middle and C-terminal regions that interact with eIF3, eIF4A, and poly(A)-binding protein. This unique architecture positions eIF4G2 as a specialized adaptor, operating outside the classic m⁷G-cap paradigm, and places it at the crossroads of translational control under both normal and stress conditions.Unlike conventional eIF4G proteins, eIF4G2 initiates translation via a cap-independent route, primarily relying on internal ribosome entry sites (IRES) within mRNA molecules. It binds directly to the 40S ribosomal subunit through eIF3, bypassing the need for eIF4E-mediated cap recognition. This mechanism is particularly vital for translating mRNAs that encode proteins involved in cell survival, apoptosis, and stress responses. For instance, eIF4G2 drives the IRES-dependent translation of pro-apoptotic factors like c-Myc and Bcl-2 under conditions where cap-dependent translation is suppressed. Its activity is tightly regulated by proteolytic cleavage and phosphorylation, ensuring that cells can swiftly reprogram their proteome in response to environmental cues or pathological insults.

Figure 1. eIF4G2 structure.

Regulatory Dynamics and Post-Translational Modifications
The functional output of eIF4G2 is heavily influenced by a cascade of post-translational modifications that modulate its stability and binding affinities. During apoptosis, caspases cleave eIF4G2 at specific sites, generating fragments that either enhance or inhibit its IRES-translation activity. Additionally, phosphorylation by kinases such as mTOR and MAPK pathways fine-tunes its interaction with eIF3 and eIF4A, adjusting translational efficiency in a context-dependent manner. These modifications allow eIF4G2 to act as a molecular switch, shifting cells between growth-promoting and stress-adaptive translational programs. Dysregulation of these modifications has been linked to aberrant cell proliferation, highlighting the importance of strict control over eIF4G2 function.

Biological Significance in Cellular Stress and Apoptosis
eIF4G2 emerges as a critical player during cellular stress, including hypoxia, nutrient deprivation, and viral infection. Under these conditions, global cap-dependent translation is attenuated, yet eIF4G2 sustains the synthesis of essential survival and death-regulatory proteins. It facilitates the translation of mRNAs harboring complex 5′ UTR structures, enabling cells to mount an appropriate adaptive response. Notably, eIF4G2 is indispensable for proper execution of apoptosis, as it promotes the production of key pro-apoptotic effectors. Conversely, its overexpression can confer resistance to certain chemotherapeutic agents by maintaining anti-apoptotic protein levels. This dual role underscores its potential as a therapeutic target, where precise modulation could tip the balance between cell survival and death.

Alternate Names for EIF4G2

EIF4G2; eukaryotic translation initiation factor 4 gamma, 2; P97; AAG1; DAP5; NAT1; eukaryotic translation initiation factor 4 gamma 2; DAP-5; eIF4G 2; eIF-4G 2; eIF-4-gamma 2; aging-associated protein 1; death-associated protein 5; eukaryotic translation initiation factor 4G-like 1;