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

作　　者：Lena Ilan Farhat Osman Lise Sarah Namer Einav Eliahu Smadar Cohen-Chalamish Yitzhak Ben-Asouli Yona Banai Raymond Kaempfer 

机构地区：[1]Department of Biochemtstry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel

出　　处：《Cell Research》2017年第5期688-704,共17页细胞研究（英文版）

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 2a （eIF2α）. We demon- strate 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 assem- bly 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; recom- binant 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, demon- strating evolutionary flexibility in how PKR activation regulates globin mRNA splicing through eIF2α phosphorylation.

关 键 词：globin mRNA splicing eIF2α phosphorylation PKR RNA activator of PKR spliceosome assembly 

分 类 号：Q[生物学]