PKR activation and eIF2α phosphorylation mediate human globin mRNA splicing at spliceosome assembly

• 来源期刊: 细胞研究（英文版）
• 年，卷（期）: 2017,（5）
• 页码范围: 688-704
• 页数: 17页
• 语种: 英文
• DOI: 10.1038/cr.2017.39

摘要

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.