Functional reconstitution of human eukaryotic translation initiation factor 3 (eIF3)

California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 12/2011; 108(51):20473-8. DOI: 10.1073/pnas.1116821108
Source: PubMed


Protein fate in higher eukaryotes is controlled by three complexes that share conserved architectural elements: the proteasome, COP9 signalosome, and eukaryotic translation initiation factor 3 (eIF3). Here we reconstitute the 13-subunit human eIF3 in Escherichia coli, revealing its structural core to be the eight subunits with conserved orthologues in the proteasome lid complex and COP9 signalosome. This structural core in eIF3 binds to the small (40S) ribosomal subunit, to translation initiation factors involved in mRNA cap-dependent initiation, and to the hepatitis C viral (HCV) internal ribosome entry site (IRES) RNA. Addition of the remaining eIF3 subunits enables reconstituted eIF3 to assemble intact initiation complexes with the HCV IRES. Negative-stain EM reconstructions of reconstituted eIF3 further reveal how the approximately 400 kDa molecular mass structural core organizes the highly flexible 800 kDa molecular mass eIF3 complex, and mediates translation initiation.

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Available from: Christopher S Fraser, Mar 20, 2014
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    • "eIF3 is a large complex comprising of 13 different subunits, termed a to m, which together represent one component of the 40S ribosomal subunit and of the much larger 43S translation PIC. The functional core of human eIF3 is composed of six subunits (eIF3a, eIF3b, eIF3c, eIF3e, eIF3f, and eIF3 h) of which only eIF3a, eIF3b, and eIF3c are conserved in all eukaryotes and represent core units to which most of the other subunits bind[23,24]. The subunits are conserved in sequence across species, suggesting a high degree of functional conservation as well. "
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    • "Furthermore, RACK1 was shown to associate with one of the eIF3 subunits in order to assemble a translation preinitiation complex in yeast (Hashem et al., 2013a; Kouba et al., 2012). Although our understanding of the molecular structure of the core of the 13 subunits eIF3 complex has progressed remarkably in recent years (e.g., Hashem et al., 2013b; Sun et al., 2011), the role of the noncore subunits remains essentially untested in an- imals. "
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    • "Despite many attempts of several groups, the overall structure of eIF3 remains somewhat obscure (7, 14, 15, 44). It seems evident that the eIF3 core is formed by the PCI/MPN octamer to which other subunits bind (14–16). "
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