Author response: Exon junction complex proteins bind nascent transcripts independently of pre-mRNA splicing in Drosophila melanogaster

Although it is currently understood that the exon junction complex (EJC) is recruited on spliced mRNA by a specific interaction between its central protein, eIF4AIII, and splicing factor CWC22, we found that eIF4AIII and the other EJC core proteins Y14 and MAGO bind the nascent transcripts of not only intron-containing but also intronless genes on Drosophila polytene chromosomes. Additionally, Y14 ChIP-seq demonstrates that association with transcribed genes is also splicing-independent in Drosophila S2 cells. The association of the EJC proteins with nascent transcripts does not require CWC22 and that of Y14 and MAGO is independent of eIF4AIII. We also show that eIF4AIII associates with both polysomal and monosomal RNA in S2 cell extracts, whereas Y14 and MAGO fractionate separately. Cumulatively, our data indicate a global role of eIF4AIII in gene expression, which would be independent of Y14 and MAGO, splicing, and of the EJC, as currently understood.

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Activation of Pre-mRNA Splicing by Human RNPS1 Is Regulated by CK2 Phosphorylation

Molecular and Cellular Biology ◽

10.1128/mcb.25.4.1446-1457.2005 ◽

2005 ◽

Vol 25 (4) ◽

pp. 1446-1457 ◽

Cited By ~ 22

Author(s):

Janeen H. Trembley ◽

Sawako Tatsumi ◽

Eiji Sakashita ◽

Pascal Loyer ◽

Clive A. Slaughter ◽

...

Keyword(s):

Nuclear Localization ◽

Phosphorylation Site ◽

Mrna Splicing ◽

Exon Junction Complex ◽

Exon Junction ◽

In Vivo Experiments ◽

Splicing Regulator ◽

Major Phosphorylation Site

ABSTRACT Human RNPS1 was originally characterized as a pre-mRNA splicing activator in vitro and was shown to regulate alternative splicing in vivo. RNPS1 was also identified as a protein component of the splicing-dependent mRNP complex, or exon-exon junction complex (EJC), and a role for RNPS1 in postsplicing processes has been proposed. Here we demonstrate that RNPS1 incorporates into active spliceosomes, enhances the formation of the ATP-dependent A complex, and promotes the generation of both intermediate and final spliced products. RNPS1 is phosphorylated in vivo and interacts with the CK2 (casein kinase II) protein kinase. Serine 53 (Ser-53) of RNPS1 was identified as the major phosphorylation site for CK2 in vitro, and the same site is also phosphorylated in vivo. The phosphorylation status of Ser-53 significantly affects splicing activation in vitro, but it does not perturb the nuclear localization of RNPS1. In vivo experiments indicated that the phosphorylation of RNPS1 at Ser-53 influences the efficiencies of both splicing and translation. We propose that RNPS1 is a splicing regulator whose activator function is controlled in part by CK2 phosphorylation.

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A Day in the Life of the Exon Junction Complex

Biomolecules ◽

10.3390/biom10060866 ◽

2020 ◽

Vol 10 (6) ◽

pp. 866 ◽

Cited By ~ 5

Author(s):

Lena P. Schlautmann ◽

Niels H. Gehring

Keyword(s):

Mrna Export ◽

Mrna Splicing ◽

Exon Junction Complex ◽

Chronological Order ◽

Exon Junction ◽

Messenger Ribonucleoprotein ◽

Associated Proteins ◽

Core Components ◽

Nonsense Mediated Mrna Decay ◽

Exon Junctions

The exon junction complex (EJC) is an abundant messenger ribonucleoprotein (mRNP) component that is assembled during splicing and binds to mRNAs upstream of exon-exon junctions. EJCs accompany the mRNA during its entire life in the nucleus and the cytoplasm and communicate the information about the splicing process and the position of introns. Specifically, the EJC’s core components and its associated proteins regulate different steps of gene expression, including pre-mRNA splicing, mRNA export, translation, and nonsense-mediated mRNA decay (NMD). This review summarizes the most important functions and main protagonists in the life of the EJC. It also provides an overview of the latest findings on the assembly, composition and molecular activities of the EJC and presents them in the chronological order, in which they play a role in the EJC’s life cycle.

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