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Mpr1p, Pad1p N-terminal (MPN) domains without catalytic isopeptidase activity, found in eIF2h Eukaryotic translation initiation factor 3 (eIF3) subunit h (eIF3h; eIF3 subunit 3; eIF3S3; eIF3-gamma; eIF3-p40) is an evolutionarily non-conserved subunit of the functional core that comprises eIF3a, eIF3b, eIF3c, eIF3e, eIF3f, and eIF3h, and contains the MPN domain. However, it lacks the canonical JAMM motif, and therefore does not show catalytic isopeptidase activity.Together with eIF3e and eIF3f, eIF3h stabilizes the eIF3 complex. Results suggest that eIF3h regulates cell growth and viability, and that over-expression of the gene may provide growth advantage to prostate, breast, and liver cancer cells. For example, EIF3h gene amplification is common in late-stage prostate cancer suggesting that it may be functionally involved in the progression of the disease. It has been shown that coamplification of MYC, a well characterized oncogene involved in cell growth, differentiation, and apoptosis, and EIF3h in patients with non-small cell lung cancer (NSCLC) improves survival if treated with the Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor (EGFR-TKI), Gefitinib. Plant eIF3h is implicated in translation of specific mRNAs. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",