A protein map of the yeast activated spliceosome as obtained by electron microscopy

SNRPB2: a prognostic biomarker and oncogenic driver in esophageal cancer via β-catenin/c-Myc signaling

Background

The SNRPB2 gene encodes Small Nuclear Ribonucleoprotein Polypeptide B2, a crucial component involved in RNA splicing processes. While SNRPB2 dysregulation has been observed in various cancers, its role in esophageal cancer (ESCA) remains unclear.

Methods

The mRNA level of SNRPB2 in ESCA was evaluated in combination with TCGA, GTEX, and GEO databases. The prognostic value of SNRPB2 was assessed using Kaplan-Meier analysis. Immunohistochemistry (IHC) was employed to confirm the expression of the SNRPB2 protein in tumor tissues from clinical samples. The biological functions of SNRPB2 were assessed in vitro cell assay and in vivo tumor models. The molecular mechanisms were determined by correlation and gene set enrichment analysis. Western blot experiments validated involvement in signaling pathways.

Results

Our findings unveiled that SNRPB2 was upregulated at both mRNA and protein levels in ESCA, which was associated with the pathological progression of the disease. Additionally, SNRPB2 served as a robust prognostic biomarker, implicated in driving oncogenic functions in ESCA. It facilitated cell proliferation, migration, and invasion, transitioned the cell cycle, and inhibited apoptosis. Mechanistically, SNRPB2 activated genes associated with the β-catenin/c-Myc signaling pathway, such as β-catenin, c-Myc, CCNA2, CCNB1, CDK1, and CDK2. This activation also regulated the epithelial-to-mesenchymal transition (EMT), thereby facilitating the progression of ESCA.

Conclusion

Our findings demonstrate that SNRPB2 contributes to ESCA progression by regulating the β-catenin/c-Myc axis, suggesting its potential as a prognostic biomarker and therapeutic target for ESCA patients.

RBM22, a Key Player of Pre-mRNA Splicing and Gene Expression Regulation, Is Altered in Cancer

RNA-Binding Proteins (RBP) are very diverse and cover a large number of functions in the cells. This review focuses on RBM22, a gene encoding an RBP and belonging to the RNA-Binding Motif (RBM) family of genes. RBM22 presents a Zinc Finger like and a Zinc Finger domain, an RNA-Recognition Motif (RRM), and a Proline-Rich domain with a general structure suggesting a fusion of two yeast genes during evolution: Cwc2 and Ecm2. RBM22 is mainly involved in pre-mRNA splicing, playing the essential role of maintaining the conformation of the catalytic core of the spliceosome and acting as a bridge between the catalytic core and other essential protein components of the spliceosome. RBM22 is also involved in gene regulation, and is able to bind DNA, acting as a bona fide transcription factor on a large number of target genes. Undoubtedly due to its wide scope in the regulation of gene expression, RBM22 has been associated with several pathologies and, notably, with the aggressiveness of cancer cells and with the phenotype of a myelodysplastic syndrome. Mutations, enforced expression level, and haploinsufficiency of RBM22 gene are observed in those diseases. RBM22 could represent a potential therapeutic target in specific diseases, and, notably, in cancer.

Biology of the mRNA Splicing Machinery and Its Dysregulation in Cancer Providing Therapeutic Opportunities

Dysregulation of messenger RNA (mRNA) processing—in particular mRNA splicing—is a hallmark of cancer. Compared to normal cells, cancer cells frequently present aberrant mRNA splicing, which promotes cancer progression and treatment resistance. This hallmark provides opportunities for developing new targeted cancer treatments. Splicing of precursor mRNA into mature mRNA is executed by a dynamic complex of proteins and small RNAs called the spliceosome. Spliceosomes are part of the supraspliceosome, a macromolecular structure where all co-transcriptional mRNA processing activities in the cell nucleus are coordinated. Here we review the biology of the mRNA splicing machinery in the context of other mRNA processing activities in the supraspliceosome and present current knowledge of its dysregulation in lung cancer. In addition, we review investigations to discover therapeutic targets in the spliceosome and give an overview of inhibitors and modulators of the mRNA splicing process identified so far. Together, this provides insight into the value of targeting the spliceosome as a possible new treatment for lung cancer.

Regulation of Prp43-mediated disassembly of spliceosomes by its cofactors Ntr1 and Ntr2

The DEAH-box NTPase Prp43 disassembles spliceosomes in co-operation with the cofactors Ntr1/Spp382 and Ntr2, forming the NTR complex. How Prp43 is regulated by its cofactors to discard selectively only intron-lariat spliceosomes (ILS) and defective spliceosomes and to prevent disassembly of earlier and properly assembled/wild-type spliceosomes remains unclear. First, we show that Ntr1΄s G-patch motif (Ntr1GP) can be replaced by the GP motif of Pfa1/Sqs1, a Prp43΄s cofactor in ribosome biogenesis, demonstrating that the specific function of Ntr1GP is to activate Prp43 for spliceosome disassembly and not to guide Prp43 to its binding site in the spliceosome. Furthermore, we show that Ntr1΄s C-terminal domain (CTD) plays a safeguarding role by preventing Prp43 from disrupting wild-type spliceosomes other than the ILS. Ntr1 and Ntr2 can also discriminate between wild-type and defective spliceosomes. In both type of spliceosomes, Ntr1-CTD impedes Prp43-mediated disassembly while the Ntr1GP promotes disassembly. Intriguingly, Ntr2 plays a specific role in defective spliceosomes, likely by stabilizing Ntr1 and allowing Prp43 to enter a productive interaction with the GP motif of Ntr1. Our data indicate that Ntr1 and Ntr2 act as ‘doorkeepers’ and suggest that both cofactors inspect the RNP structure of spliceosomal complexes thereby targeting suboptimal spliceosomes for Prp43-mediated disassembly.