EUKARYOTIC TRANSLATION INITIATION FACTOR 1A, X-LINKED; EIF1AX

Alternative titles; symbols

• EUKARYOTIC TRANSLATION INITIATION FACTOR 1A; EIF1A
• EUKARYOTIC TRANSLATION INITIATION FACTOR 4C; EIF4C

HGNC Approved Gene Symbol: EIF1AX

Cytogenetic location: Xp22.12 Genomic coordinates (GRCh38): X:20,124,524-20,141,837 (from NCBI)

▼ Description

The small eukaryotic initiation factor eIF4C is implicated in the translation initiation pathway, where it enhances ribosome dissociation into subunits and stabilizes the binding of the initiator Met-tRNA to 40S ribosomal subunits (summary by Dever et al., 1994).

▼ Cloning and Expression

Dever et al. (1994) purified rabbit eIF4C and determined its amino acid sequence. By PCR with degenerate primers based on the rabbit eIF4C sequence, they isolated a partial human leukemia cDNA encoding eIF4C. They screened a leukemia cDNA library with the partial cDNA and obtained additional clones corresponding to the entire human eIF4C coding region. The sequence of the predicted 144-amino acid human protein was identical to that of rabbit eIF4C except in a single position. The human protein had an unblocked N-terminal proline, which Dever et al. (1994) stated was consistent with the general pattern of eukaryotic protein processing that removes an initiating methionine when it is followed by a proline. Sequence analysis revealed that eIF4C has a polar structure, with 9 of the first 15 amino acids being basic and 13 of the last 20 amino acids being acidic. The authors suggested that the dipole nature of the protein may allow it to interact with 2 different types of surfaces, perhaps functioning as a bridge between 2 initiation factors or between an initiation factor and the ribosome.

▼ Biochemical Features

Crystal Structure

Lomakin and Steitz (2013) determined the crystal structures of 3 complexes of the small ribosomal subunit 40S that represent distinct steps in mammalian translation initiation. These structures revealed the location of eIF1, eIF1A, mRNA, and initiator transfer RNA (see 180621) bound to the small ribosomal subunit and provided insights into the details of translation initiation specific to eukaryotes. Conformational changes associated with the captured functional states revealed the dynamics of the interactions of the P site of the ribosome.

▼ Mapping

Lahn and Page (1997) mapped the EIF1A gene to the X chromosome by analysis of a somatic cell hybrid panel. They designated this gene EIF1AX to distinguish it from the Y-linked homolog, EIF1AY (400014). Lahn and Page (1997) determined that the EIF1AX gene escapes X inactivation, and proposed that it should be investigated as a candidate gene for Turner syndrome. See 400010.