EIF3Eukaryotic Initiation Factor-3
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Compared with subtype 1b, HCV 6a has a modified eIF3 binding site within hairpin III.[sup][20] It is reported that hepatic iron levels are higher in patients infected with subtype 1b than those in patients infected with subtypes 2a or 2b, which may explain the different responses of HCV genotypes to iron overload.[sup][57]
Regulation of hepatitis C virus translation initiation by iron: Role of eIF3 and La protein.
Picornavirus IRES elements are the examples of types I and II IRESes which require eIF4G, eIF4A, and eIF3 to assemble 48S initiation complex [29].
For example, the Lmyc IRES requires the eIF4F complex and interaction of both poly(A) tail binding protein (PABP) and eIF3 with eIF4G for translation [20].
The eIF5B-eIF3 mediated mechanism involves eIF3 stimulating tRNAi binding to the 40S subunit (in the IRES/40S complex) in an eIF5B-dependent manner, which allows for the formation of the 48S initiation complex and, subsequently, the translation-competent 80S ribosome [30].
A recent study suggests that eIF3 subunit d plays a key role in alternative mechanisms of translation initiation by a noncanonical mechanism of cap recognition.
DAP5 domains share homology with the central and C-terminal region of eIF4G that interacts with eIF4A, eIF3, Mnk1, and eIF2fi but not eIF4E [42].
eIF3. Eukaryotic initiation factor 3 (eIF3) is a 13-subunit complex of 800 kilodaltons, required for translation initiation through interactions with the 40S ribosomal subunit, mRNA, and other eIFs necessary for the formation of competent translation initiation complexes [19, 114].
In addition to the critical function of the eIF3 complex in translation initiation, many eIF3 subunits have been shown to be involved in a diverse set of cellular processes including apoptosis, oncogenesis, and cellular growth and proliferation [89, 100, 109, 114, 120-122].
This enhancement of translation rates for these proteins and subsequent production of malignant phenotypes may not be a direct consequence of the overexpression of a single eIF3 subunit since enhanced levels of other eIF3 subunits (a, b, c, f, h, and j) were also noted.
Like other eIF3 subunits, eIF3d is also involved in protein synthesis and has been shown to be upregulated in gastric cancer and mesothelioma [70,104].
While it is possible for the IRES to independently interact with the 40S and 60S ribosomal subunits, canonical translation factors (e.g., eIF4A and eIF3) and IRES-transacting factors (ITAFs) are usually involved to enhance translation efficiency.