MEHMO syndrome mutation EIF2S3-I259M impairs initiator Met-tRNAiMet binding to eukaryotic translation initiation factor eIF2. Issue 2 (4th December 2018)

• Record Type: Journal Article
• Authors: Young-Baird, Sara K; Shin, Byung-Sik; Dever, Thomas E
• Is Part Of: Nucleic acids research. Volume 47:Issue 2(2019)
• Page Start: 855
• Page End: 867
• Publication Date: 2018-12-04
• Subjects: Nucleic acids -- Periodicals; Molecular biology -- Periodicals; 572.805
• DOI: 10.1093/nar/gky1213
• Languages: English
• ISSNs: 0305-1048

Abstract

Abstract: The heterotrimeric eukaryotic translation initiation factor (eIF) 2 plays critical roles in delivering initiator Met-tRNAi Met to the 40S ribosomal subunit and in selecting the translation initiation site. Genetic analyses of patients with MEHMO syndrome, an X-linked intellectual disability syndrome, have identified several unique mutations in the EIF2S3 gene that encodes the γ subunit of eIF2. To gain insights into the molecular consequences of MEHMO syndrome mutations on eIF2 function, we generated a yeast model of the human eIF2γ-I259M mutant, previously identified in a patient with MEHMO syndrome. The corresponding eIF2γ-I318M mutation impaired yeast cell growth and derepressed GCN4 expression, an indicator of defective eIF2–GTP–Met-tRNAi Met complex formation, and, likewise, overexpression of human eIF2γ-I259M derepressed ATF4 messenger RNA translation in human cells. The yeast eIF2γ-I318M mutation also increased initiation from near-cognate start codons. Biochemical analyses revealed a defect in Met-tRNAi Met binding to the mutant yeast eIF2 complexes in vivo and in vitro . Overexpression of tRNAi Met restored Met-tRNAi Met binding to eIF2 in vivo and rescued the growth defect in the eIF2γ-I318M strain. Based on these findings and the structure of eIF2, we propose that the I259M mutation impairs Met-tRNAi Met binding, causing altered control of protein synthesis that underlies MEHMO syndrome.