RBMX2

RBMX2 is the central scaffold subunit of the trimeric RES (retention and splicing) complex, functioning in pre-mRNA splicing by promoting the progression of spliceosome assembly toward catalytic activation (PMID:11287609, PMID:29330354). Its yeast ortholog Snu17 directly binds Bud13 and recruits Pml1, with hierarchical protein-protein contacts defining the architecture of the RES complex (PMID:19033360). Mechanistically, RES is required for efficient transformation of the precatalytic B spliceosome into the activated Bact complex; in its absence, recruitment of Pml1 and Bud13 to the spliceosome is lost and the splicing helicase Prp2 binds prematurely and disassembles the structurally compromised complexes, defining a checkpoint at B-to-Bact activation (PMID:29330354). In vertebrates, RBMX2/RES is specifically required for splicing of short, GC-rich introns defined by intron definition, and its loss causes widespread mis-splicing, increased neural cell death, and impaired neuronal differentiation during early development (PMID:29969449). Beyond its core splicing role, RBMX2 binds APAF-1 pre-mRNA to drive intron-retention alternative splicing and promote apoptosis (PMID:39308873), and modulates cell adhesion and epithelial-mesenchymal transition via p65/MMP-9 signaling during bacterial infection (PMID:33718289, PMID:41277807).

1. 2001 High

   Established that the RBMX2 ortholog is a U2 snRNP-associated factor needed to advance spliceosome assembly, answering whether it acts before or during catalysis.

   Evidence Protein microsequencing, snRNP co-IP, native-gel spliceosome assembly, and in vitro splicing complementation with recombinant Snu17p in yeast

   PMID:11287609

   Open questions at the time

   • Did not define the protein partners that anchor Snu17 within the spliceosome
   • Vertebrate function not addressed
2. 2008 High

   Resolved the internal architecture of the RES complex, showing RBMX2/Snu17 is the scaffold that bridges Bud13 and Pml1.

   Evidence X-ray crystallography of Pml1, recombinant sub-complex reconstitution, serial truncation/mutagenesis, and splice-site choice assays

   PMID:19033360

   Open questions at the time

   • Did not show how RES engages the assembling spliceosome
   • Pml1 FHA phosphothreonine pocket dispensable, leaving its functional contribution unclear
3. 2012 Medium

   Connected RES splicing activity to a specific cell-fate output by showing Snu17 is required to splice MATa1 pre-mRNA controlling cell-type identity.

   Evidence Genetic deletion, in vivo splicing analysis, epistasis with axl1, and bud-site selection assay in diploid yeast

   PMID:23118884

   Open questions at the time

   • Substrate specificity determinants not defined
   • Single-lab genetic study
4. 2018 High

   Defined the precise step RBMX2/RES controls, showing it is required for B-to-Bact transition and that its loss exposes spliceosomes to premature Prp2-mediated disassembly.

   Evidence Affinity purification of yeast spliceosomes, native-gel assembly analysis, and in vitro disassembly with recombinant Prp2/Spp2/UTP

   PMID:29330354

   Open questions at the time

   • Molecular basis of Prp2 proofreading recognition not detailed
   • Yeast-based; vertebrate mechanism inferred separately
5. 2018 High

   Extended RBMX2 function to vertebrates, identifying the intron features it acts on and linking its loss to neural developmental defects.

   Evidence CRISPR/Cas9 loss-of-function in zebrafish, transcriptome-wide RNA-seq splicing analysis, and computational modeling of RES-dependent introns across three RES subunit mutants

   PMID:29969449

   Open questions at the time

   • Mechanism linking mis-splicing to neural cell death not resolved
   • Direct RNA targets in mammals not enumerated
6. 2021 Medium

   Identified a pathogen-derived interactor of RBMX2, implicating the protein in host-pathogen interaction beyond canonical splicing.

   Evidence Yeast two-hybrid, co-IP, BiFC, and confocal co-localization in HEK293T cells with Theileria annulata TA05575

   PMID:33718289

   Open questions at the time

   • Functional consequence of the interaction not established
   • Single lab, heterologous cell system
7. 2024 Medium

   Linked RBMX2 to apoptosis regulation by showing it drives intron-retention alternative splicing of APAF-1 during bacterial infection.

   Evidence RBMX2 knockout in EBL cells, transcriptome and alternative-splicing sequencing, molecular docking/dynamics, and RT-qPCR in M. bovis infection

   PMID:39308873

   Open questions at the time

   • RBMX2-APAF-1 binding shown computationally, not biochemically reconstituted
   • Single-lab, infection-specific context
8. 2025 Medium

   Implicated RBMX2 in cell adhesion and EMT, showing it suppresses tight-junction formation and promotes invasion via p65/MMP-9 signaling.

   Evidence Multi-omics, cell adhesion assays, ChIP-PCR, Western blot, and immunofluorescence in M. bovis EMT models

   PMID:41277807

   Open questions at the time

   • Mechanism connecting splicing scaffold function to p65 activation unclear
   • Single lab, infection-context only

• How RBMX2's core role as a splicing scaffold mechanistically gives rise to its reported infection-associated roles in apoptosis, adhesion, and EMT remains unresolved.
• No structural model of the vertebrate RES complex on the spliceosome
• Direct mammalian RNA targets not comprehensively mapped
• Causal link between splicing scaffold activity and p65/MMP-9 signaling not established