RSRC1

RSRC1 (SRrp53) is an SR-related nuclear protein that couples pre-mRNA splicing to transcriptional regulation and is essential for normal neurodevelopment (PMID:15798186, PMID:29522154). In nuclear speckles it acts as a splicing factor specifically required for the second catalytic step of pre-mRNA splicing, functioning through interactions with the Luc7p ortholog, the U2AF65-related factor HCC1, SR-family proteins, and U2AF35, and it modulates alternative splice-site choice in a concentration-dependent manner (PMID:15798186). Beyond constitutive splicing, RSRC1 regulates gene expression: it represses estrogen receptor β transcriptional activity by promoting PIAS1-dependent SUMOylation of ERβ in a manner that itself depends on RSRC1 SUMOylation (PMID:25937118), and it sustains expression of targets including PTEN and IGFBP3 (PMID:29522154, PMID:31257492). Loss-of-function RSRC1 mutations that trigger nonsense-mediated decay cause autosomal recessive intellectual disability with hypotonia and mild dysmorphism, linked to aberrant splicing and transcription in patient-derived neural progenitors (PMID:29522154).

1. 2005 High

   Established that RSRC1/SRrp53 is a functional splicing factor by defining its specific requirement in the second catalytic step and its spliceosomal interaction network, answering whether the protein had a direct biochemical role in splicing.

   Evidence Immunodepletion/reconstitution of splicing in HeLa nuclear extracts with recombinant rescue, plus yeast two-hybrid and co-IP mapping of interactions with Luc7p ortholog, HCC1, SR proteins, and U2AF35

   PMID:15798186

   Open questions at the time

   • Structural basis of second-step participation not resolved
   • No genome-wide map of endogenous splicing targets
   • Concentration-dependence of alternative splicing not linked to specific transcripts
2. 2015 Medium

   Extended RSRC1 function from splicing to transcriptional control by showing it represses ERβ via SUMO-dependent regulation, revealing a SUMOylation-gated coregulator activity.

   Evidence Co-IP, SUMOylation assays, transcriptional reporters, and mutagenesis of RSRC1 SUMO sites

   PMID:25937118

   Open questions at the time

   • Single lab, not independently confirmed
   • Direct vs. indirect bridging of ERβ to PIAS1 unclear
   • Generality beyond ERβ not tested
3. 2018 High

   Linked RSRC1 loss to autosomal recessive intellectual disability and connected the disease mechanism to aberrant splicing and transcription, establishing physiological importance in neurodevelopment.

   Evidence Homozygosity mapping, exome sequencing, NMD confirmation in patient fibroblasts, shRNA silencing/overexpression in SH-SY5Y cells with transcriptome profiling, and patient iPSC-derived neural progenitor validation

   PMID:29522154

   Open questions at the time

   • Causal splicing events driving the neuronal phenotype not pinpointed
   • Mechanism connecting RSRC1 loss to IGFBP3 downregulation not resolved
   • No rescue in patient neurons
4. 2019 Medium

   Implicated RSRC1 as a tumor suppressor in gastric cancer by tying its loss to increased proliferation/migration and reduced PTEN, addressing whether RSRC1 has growth-regulatory function.

   Evidence siRNA knockdown in gastric cancer cells with proliferation, EdU, and Transwell assays plus PTEN Western blot and RT-qPCR

   PMID:31257492

   Open questions at the time

   • No rescue or epistasis experiment
   • Whether PTEN regulation is via splicing or transcription not determined
   • In vivo tumor relevance untested
5. 2025 Medium

   Identified RSRC1 as an evolutionarily conserved modulator of aging by showing ortholog knockdown extends lifespan, raising the possibility of a conserved organismal function.

   Evidence Post-developmental RNAi of spch-2 in C. elegans with replicated lifespan assays

   PMID:41078088

   Open questions at the time

   • Relevance to mammalian RSRC1 inferred only by orthology
   • Molecular pathway linking RSRC1 to longevity unknown
   • Whether splicing or transcription drives the lifespan effect untested

• How RSRC1's splicing activity, SUMO-dependent transcriptional coregulation, and target gene control (PTEN, IGFBP3, ERβ) mechanistically integrate into a single biochemical program remains unresolved.
• No unifying mechanism connecting splicing and transcription roles
• No structural model of RSRC1
• Direct endogenous RNA and protein targets not comprehensively mapped