| Category | Key claim | Evidence type | Quantitative/statistical details | Primary source with year and DOI URL | Citation ID placeholder |
|---|---|---|---|---|---|
| Canonical SRP function | SRP9 forms an obligate SRP9/14 heterodimer that clamps the 5′ and 3′ ends of the Alu domain RNA, stabilizing the closed ribosome-stalling conformation required for translational slowdown during co-translational targeting. | Structure | Human Alu RNP crystal structure solved at 2.0 Å; SRP9 contributes ~700 Ų of protein-RNA interface within a total ~1,820 Ų SRP9/14-RNA interface; docking places the complex at the elongation factor-binding site. | Ahl et al., 2015, Molecular Cell. https://doi.org/10.1016/j.molcel.2015.10.003 | (pqac-00000040, pqac-00000039, pqac-00000045) |
| Canonical SRP function | In mammalian scanning and engaged SRP-ribosome states, the SRP9/14-containing Alu domain sits at the ribosomal GTPase center, where it can compete with elongation factors and prolong the targeting window. | Cryo-EM structure/biochemical competition | Hbs1-DN displaced SRP from scanning ribosome-nascent chain complexes by up to ~70% but not from engaged complexes, supporting dynamic Alu competition at the factor-binding center. | Voorhees & Hegde, 2015, eLife. https://doi.org/10.7554/eLife.07975 | (pqac-00000032, pqac-00000035, pqac-00000036) |
| Canonical SRP function | SRP9/14 is not the dominant ribosome affinity determinant for human SRP; SRP54 and SRP68/72 account for most measurable binding, while the Alu domain contributes little or only slightly in reconstituted assays. | MST binding/reconstitution | Full SRP binds in the (sub-)nanomolar range; isolated SRP54 KD ~30 nM; SRP68/72 KD ~160 ± 20 nM with Hill coefficient ~2.3; SR heterodimer KD 410 ± 50 nM; Alu contribution not quantifiable or minor. | Wild et al., 2019, Nucleic Acids Research. https://doi.org/10.1093/nar/gky1324 | (pqac-00000024, pqac-00000025, pqac-00000026, pqac-00000029, pqac-00000030) |
| SRP biogenesis/localization | SRP9/14 participates in nuclear/nucleolar phases of SRP assembly; most SRP proteins assemble with 7SL in the nucleus/nucleolus before final cytoplasmic maturation. | Review of assembly data/in vitro assembly | Ordered assembly summarized as SRP19 → SRP68/72 → SRP9/14 on 7SL RNA before cytoplasmic completion with SRP54. | Kellogg et al., 2021, Int J Mol Sci. https://doi.org/10.3390/ijms22126284 | (pqac-00000007, pqac-00000011) |
| SRP biogenesis/localization | GFP-SRP9 is found mostly in the nucleus with faint cytoplasmic signal; SRP9/14 heterodimer accumulates in nucleoplasm, and nucleolar integrity is required for proper SRP protein localization. | Microscopy, GFP-trap IP, SILAC proteomics | Study identified 95 newly found nucleolar/ribosome-biogenesis-related SRP interactors, bringing total SRP-associated nucleolar/ribosome biogenesis factors to 173. | Issa et al., 2024, Life Science Alliance. https://doi.org/10.26508/lsa.202402614 | (pqac-00000009, pqac-00000012, pqac-00000014) |
| SRP biogenesis/localization | In SR receptor knockout cells, SRP9 protein remains present and SRP complex composition is retained, indicating SR loss does not collapse SRP abundance. | TMT-SILAC proteomics | In membrane proteome analysis, only ~25% of 287 polytopic and ~20% of 350 single-pass membrane proteins were downregulated; SRP9, SRP14, SRP19, SRP54, SRP68, SRP72 were still detected in both channels. | Child et al., 2023, RNA. https://doi.org/10.1261/rna.079643.123 | (pqac-00000063) |
| Alu/retrotransposition | SRP9/14-bound Alu RNP mimics the SRP Alu domain and occupies the ribosomal elongation factor-binding site, linking ribosome stalling to Alu retrotransposition. | Structure/mutagenesis/retrotransposition assays | PDB 5AOX; mutations weakening SRP9/14 interaction by >3.5 kcal/mol abolish retrotransposition; exemplar constructs showed ~111%, 11%, and 83% relative activities depending on retained folding features. | Ahl et al., 2015, Molecular Cell. https://doi.org/10.1016/j.molcel.2015.10.003 | (pqac-00000041, pqac-00000042, pqac-00000046, pqac-00000047) |
| Alu/retrotransposition | SRP9/14 binds 7SL and related Alu RNAs with high affinity and exists in substantial molar excess over assembled SRP, enabling extensive extra-canonical regulation of Alu-family RNAs. | Review synthesis of primary biochemical studies | Human SRP9/14 binds 7SL with sub-nanomolar affinity; primate SRP9/14 is present at ~20-fold molar excess over intact SRP; Alu elements comprise ~10% of the human genome. | Gussakovsky et al., 2024, RNA Biology. https://doi.org/10.1080/15476286.2024.2430817 | (pqac-00000005, pqac-00000001) |
| Splicing regulation | SRP9/14 binds compact/closed Alu RNA conformations and modulates exonization of Alu-derived exons, acting functionally like an RNA chaperone in pre-mRNA splicing decisions. | Structure-guided mutagenesis, pull-down/immunoblot, footprinting, RNAi splicing assays | Splicing analysis covered 38 reporters; ~15 endogenous transcripts screened; six additional endogenous SRP9/14-regulated Alu exons identified; 16.5 µg recombinant SRP9/14 used in footprinting; SRP9/14 is ~20-fold in excess over SRP. | Borovská et al., 2023, Nucleic Acids Research. https://doi.org/10.1093/nar/gkad500 | (pqac-00000057, pqac-00000058, pqac-00000059, pqac-00000062) |
| SRP biogenesis/localization | Nuclear SRP9/SRP14 positively regulates steady-state 7SL and BC200 levels by promoting transcription rather than RNA stability. | ChIP-qPCR, siRNA knockdown, BRIC/actinomycin D decay assays, fractionation | 7SL reduced ~40% by 72 h knockdown; BC200 reduced >80% by 48 h and ~95% by 72 h; 7SL half-life 1.7 h (95% CI 1.4–2.1), BC200 1.5 h (95% CI 1.3–1.6); Pol III occupancy at 7SL fell ~15% at 48 h (P=1.3×10^-2) and ~15% at 72 h (P=6.5×10^-5); BC200 occupancy fell 15% (P=6.8×10^-3), 32% (P=2.0×10^-3), 48% (P=1.9×10^-4). | Gussakovsky et al., 2023, RNA. https://doi.org/10.1261/rna.079649.123 | (pqac-00000050, pqac-00000051, pqac-00000052, pqac-00000053, pqac-00000056) |
| Disease/biomarker | In pancreatic ductal adenocarcinoma, higher nuclear SRP9 localization is associated with better recurrence-free survival and with distinct translation/cancer-pathway RNA associations. | IHC, immunocytochemistry, splice-variant transfection, RIP-seq | Surgical cohort n=38; >50% nuclear-staining group n=24 vs ≤50% group n=14; better RFS P=0.037; OS not significant P=0.604; Ki-67 correlation R²=0.007, P=0.622; lymphatic invasion distribution differed (ly0:ly1 = 5:9 vs 17:7, P=0.047); amino-acid deficiency lowered nuclear translocation with P<0.0001 in cell assays. | Sato et al., 2024, International Journal of Oncology. https://doi.org/10.3892/ijo.2024.5662 | (pqac-00000016, pqac-00000017, pqac-00000018, pqac-00000021, pqac-00000023) |
| Disease/biomarker | Public genetics/functional-association resources connect SRP9 to several disease areas, but current evidence is indirect and driven largely by functional-genomics datasets rather than established clinical causality. | Database association/functional genomics aggregation | Open Targets scores: neurodegenerative disease 0.542; abnormality of skeletal system 0.450; osteoarthritis 0.413; osteoarthritis, knee 0.331; lysosomal storage disease 0.109; evidence count 5 per listed association. | Open Targets Platform query for SRP9, accessed via tool context. https://platform.opentargets.org | (pqac-00000000) |


*Table: This table summarizes the strongest mechanistic, localization, regulatory, and disease-linked evidence for human SRP9 (UniProt P49458). It emphasizes the distinction between canonical SRP/Alu-domain functions and emerging nuclear, splicing, and biomarker-related roles supported by recent literature and database evidence.*