PKR Activation and EIF2α Phosphorylation Mediate Human Globin MRNA Splicing at Spliceosome Assembly

Overview

Journal Cell Res

Specialty Cell Biology

Date 2017 Apr 5

PMID 28374749

Citations 20

Authors

Lena Ilan

Farhat Osman

Lise Sarah Namer

Einav Eliahu

Smadar Cohen-Chalamish

Yitzhak Ben-Asouli

Yona Banai

Raymond Kaempfer

Affiliations

Soon will be listed here.

Abstract

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.

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