NCBP3 positively impacts mRNA biogenesis

Abstract

The nuclear Cap-Binding Complex (CBC), consisting of Nuclear Cap-Binding Protein 1 (NCBP1) and 2 (NCBP2), associates with the nascent 5′cap of RNA polymerase II transcripts and impacts RNA fate decisions. Recently, the C17orf85 protein, also called NCBP3, was suggested to form an alternative CBC by replacing NCBP2. However, applying protein–protein interaction screening of NCBP1, 2 and 3, we find that the interaction profile of NCBP3 is distinct. Whereas NCBP1 and 2 identify known CBC interactors, NCBP3 primarily interacts with components of the Exon Junction Complex (EJC) and the TRanscription and EXport (TREX) complex. NCBP3-EJC association in vitro and in vivo requires EJC core integrity and the in vivo RNA binding profiles of EJC and NCBP3 overlap. We further show that NCBP3 competes with the RNA degradation factor ZC3H18 for binding CBC-bound transcripts, and that NCBP3 positively impacts the nuclear export of polyadenylated RNAs and the expression of large multi-exonic transcripts. Collectively, our results place NCBP3 with the EJC and TREX complexes in supporting mRNA expression.

Cytoplasmic Switch of ARS2 Isoforms Promotes Nonsense-Mediated mRNA Decay and Arsenic Sensitivity

“…We know from previous work that ARS2n interacts with all four core components of the EJC: CASC3, MAGOH, RBM8A and EIF4A3, the EJC periferal factors: UPF3B, RNPS1, PNN and ACINUS as well as UPF1 and the phosphatases PPP2R1A and PPP2R2A (Fig. 4E) 5,19,20,43–46 . Additionally, the CBC complex (NCBP1/2) has been shown to stabilize the interaction between UPF1-ERF1/ERF3 and the EJC, promoting NMD 9,18 .…”

“…8). As previously described, ARS2n primarily functions in the nucleus in conjunction with the CBC to promote mRNA splicing, degradation and export [1][2][3][4][5][6][7] . We propose that once in the cytoplasm, an isoform switch occurs in which ARS2c replaces ARS2n within the CBC.…”

“…Previous work has shown that CBC complex component NCBP1 promotes NMD in the cytoplasm 9,18 . Additional studies have reported the interaction between ARS2 and several components of the NMD pathway 5,19,20 . However, the question of whether ARS2 participates in NMD has not been addressed.…”

“…The differential biological roles of ARS2 isoforms is evidenced in the regulation of NMD, where our data shows that both ARS2n and ARS2c work in tandem to modulate the pathway. ARS2n primarily functions in the nucleus with the CBC to regulate mRNA splicing, degradation, and export [1][2][3][4][5][6][7] . We propose that, once the mRNPs enter the cytoplasm, an isoform switch occurs in which ARS2c replaces ARS2n within the CBC.…”

Role of CCCH-Type Zinc Finger Proteins in Human Adenovirus Infections

“…The TREX complex interacts with the mRNA capping complex and the exon junction complex (EJC), thereby integrating TREX to the nuclear export pathway of capped and spliced mRNAs [ 53 ]. This also explains why the ZC3H11A protein is found to interact with various mRNA capping and splicing factors [ 56 , 57 ]. Despite the fact that the ZC3H11A protein co-purifies with the individual members of the TREX complex, its exact role in the complex still remains, to a large extent, enigmatic.…”