Abstract
Translation initiation factor 1A stimulates 40S-binding of the eukaryotic initiation factor 2 (eIF2)/GTP/Met-tRNAiMet ternary complex (TC) and promotes scanning in vitro. eIF1A contains an OB-fold present in bacterial IF1 plus N- and C-terminal extensions. Truncating the C-terminus (ΔC) or mutating OB-fold residues (66-70) of eIF1A reduced general translation in vivo but increased GCN4 translation (Gcd- phenotype) in a manner suppressed by overexpressing TC. Consistent with this, both mutations diminished 40S-bound TC, eIF5 and eIF3 in vivo, and ΔC impaired TC recruitment in vitro. The assembly defects of the OB-fold mutation can be attributed to reduced 40S-binding of eIF1A, whereas ΔC impairs eIF1A function on the ribosome. A substitution in the C-terminal helix (98-101) also reduced 43S assembly in vivo. Rather than producing a Gcd- phenotype, however, 98-101 impairs GCN4 derepression in a manner consistent with defective scanning by reinitiating ribosomes. Indeed, 98-101 allows formation of aberrant 48S complexes in vitro and increases utilization of non-AUG codons in vivo. Thus, the OB-fold is crucial for ribosome-binding and the C-terminal domain of eIF1A has eukaryotic-specific functions in TC recruitment and scanning.
Original language | English (US) |
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Pages (from-to) | 3588-3601 |
Number of pages | 14 |
Journal | EMBO Journal |
Volume | 24 |
Issue number | 20 |
DOIs | |
State | Published - Oct 19 2005 |
Externally published | Yes |
Keywords
- GCN4
- Scanning
- Translation
- eIF1A
- eIF2
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology