A multifactor complex of eukaryotic initiation factors, eIF1, eIF2, eIF3, eIF5, and initiation tRNA(super.Met) is an important translation initiation intermediate in vivo

Article Abstract:

A multifactor complex has been found to be an important translation initiation intermediate in vivo. Translation initiation factor 2 (eIF2) bound to GTP. transfers an initiator to the 40S ribosomal subunit. It has been shown that yeast eIF5 can bridge interaction in vitro between eIF3 and eIF2 by binding at the same time to the amino terminus of eIF3 subunit NIP1 and the amino-terminal half of eIF2(beta). This is dependent on a conserved two-part motif in the eIF5 carboxyl terminus.

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eIF2 independently binds two distinct eIF2B subcomplexes that catalyze and regulate guanine-nucleotide exchange

Article Abstract:

An eIF2B subcomplex of the GCN3, GCD7, and GCD2 subunits binds to eIF2 and has greater affinity for iEF2(alphaP), but has no nucleotide-exchange activity. GCD1 and GCD6 subunits form an eIF2B subcomplex that binds to eIF2 and eIF2(alphaP) equally. The latter subcomplex has greater nucleotide-exchange activity than wild-type eIF2B not held back by eIF2(alphaB). It seems that binding of eIF2(alphaB) to the regulatory subcomplex makes productive interaction impossible with the catalytic subcomplex. Independently, eIF2 binds distinct eIF2B subcomplexes that catalyze and regulate guanine-nucleotide exchange.

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The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA

Article Abstract:

Initiator methionyl tRNA maturation requires Gcd10p and Gcd14p, essential proteins that are subunits of a complex in which nuclear localization is prominent. Gcd10 mutants are defective in maturation of tRNA-Met. In addition, 1-methyladenosine formation in yeast tRNA requires Gcd10p. The need for 1-methyladenosine at position 58 may account for the role played by the Gcd10p-Gcd14p complex in the initiation phase of translation.

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