Volume 27, No 5, May 2017
ISSN: 1001-0602
EISSN: 1748-7838 2018
impact factor 17.848*
(Clarivate Analytics, 2019)
Volume 27 Issue 5, May 2017: 688-704
ORIGINAL ARTICLES
PKR activation and eIF2α phosphorylation mediate human globin mRNA splicing at spliceosome assembly
Lena Ilan1,*, Farhat Osman1,*, Lise Sarah Namer1,*, Einav Eliahu1, Smadar Cohen-Chalamish1, Yitzhak Ben-Asouli1, Yona Banai1 and Raymond Kaempfer1
1Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
Correspondence: Raymond Kaempfer, Tel: +972 2 6758389(kaempfer@hebrew.edu)
Short elements in mammalian mRNA can control gene expression by activating the RNA-dependent protein kinase PKR that attenuates translation by phosphorylating cytoplasmic eukaryotic initiation factor 2α (eIF2α). We demonstrate a novel, positive role for PKR activation and eIF2α phosphorylation in human globin mRNA splicing. PKR localizes in splicing complexes and associates with splicing factor SC35. Splicing and early-stage spliceosome assembly on β-globin pre-mRNA depend strictly on activation of PKR by a codon-containing RNA fragment within exon 1 and on phosphorylation of nuclear eIF2α on Serine 51. Nonphosphorylatable mutant eIF2αS51A blocked β-globin mRNA splicing in cells and nuclear extract. Mutations of the β-globin RNA activator abrogated PKR activation and profoundly affected mRNA splicing efficiency. PKR depletion abrogated splicing and spliceosome assembly; recombinant PKR effectively restored splicing. Excision of the first intron of β-globin induces strand displacement within the RNA activator of PKR by a sequence from exon 2, a structural rearrangement that silences the ability of spliced β-globin mRNA to activate PKR. Thus, the ability to activate PKR is transient, serving solely to enable splicing. α-Globin pre-mRNA splicing is controlled likewise but positions of PKR activator and silencer are reversed, demonstrating evolutionary flexibility in how PKR activation regulates globin mRNA splicing through eIF2α phosphorylation.
10.1038/cr.2017.39
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