| Functional role | Key experimental evidence/assay | Quantitative/conditional details | Domain/motif requirement | Primary source with DOI URL and publication date/year |
|---|---|---|---|---|
| Translation repression | Sbp1 overexpression reduced polysomes and promoted formation/localization of P-body markers, consistent with repression of translation initiation and mRNP remodeling (pqac-00000003, pqac-00000005) | Dhh1p localized to P-bodies in **80% of cells** on Sbp1 overexpression (n=78); in glucose, Dhh1p was diffuse/rarely in P-bodies in **90% of cells** (n=40). Dcp2p-GFP-marked P-bodies were small in **73% of cells** at baseline (n=56) and increased on Sbp1 overexpression in **79% of cells** (n=67) (pqac-00000003) | RGG box and RRMs are part of Sbp1 architecture; specific domain requirement for this phenotype not resolved in Segal 2006 (pqac-00000005, pqac-00000006) | Segal SP, Dunckley T, Parker R. *Molecular and Cellular Biology* (Jul 2006). DOI: https://doi.org/10.1128/MCB.01913-05 (pqac-00000003, pqac-00000005) |
| Decapping modulation | High-copy/overexpressed Sbp1 suppressed conditional decapping defects and accelerated decay of MFA2pG reporter in decapping mutants, indicating Sbp1 can enhance decapping under sensitized conditions (pqac-00000004, pqac-00000007) | MFA2pG half-life changed from **~12 min to ~6 min** in **dcp2-7** with Sbp1 overexpression and was **~8 min** in **dcp1-2** upon Sbp1 overexpression; effects were not due to altered deadenylation. sbp1Δ alone did **not** alter normal MFA2pG/PGK1pG decay (pqac-00000004) | No specific motif requirement established in this assay; mechanistic models implicate RNA-binding regions and eIF4E/eIF4G-associated functions (pqac-00000005) | Segal SP, Dunckley T, Parker R. *Molecular and Cellular Biology* (Jul 2006). DOI: https://doi.org/10.1128/MCB.01913-05 (pqac-00000004, pqac-00000005) |
| P-body localization | Fluorescence microscopy of SBP1-GFP showed stress-dependent accumulation in P-bodies; Sbp1 is cytoplasmic in log phase and relocalizes under glucose deprivation/high cell density or overexpression (pqac-00000005, pqac-00000007) | Localization occurs under stress rather than mid-log growth; overexpression increases P-body size/number and mRNA targeting to P-bodies (pqac-00000003, pqac-00000005) | Specific localization determinant not assigned in Segal 2006; later work links condensate behaviors to RGG motif-dependent functions (pqac-00000000) | Segal SP, Dunckley T, Parker R. *Molecular and Cellular Biology* (Jul 2006). DOI: https://doi.org/10.1128/MCB.01913-05 (pqac-00000003, pqac-00000005, pqac-00000007) |
| P-body disassembly | Live-cell microscopy after stress/recovery showed Δsbp1 cells are defective in disassembly of Edc3-, Dhh1-, and Scd6-marked P-bodies; complementation and in vitro reconstitution support Sbp1 as a disassembly factor (pqac-00000000, pqac-00000001, pqac-00000002) | Stress: **0.5% sodium azide for 30 min at 30°C**; recovery: **1 h**. Quantified as foci/cell, mean ± SEM, **n=4** independent experiments. Significant recovery defects in Δsbp1: **Edc3 P=0.0002** (and endogenously tagged Edc3 **P=0.021**), **Dhh1 P=0.0125**, **Scd6 P=0.0132** (pqac-00000001, pqac-00000012) | **RGG motif required**: SBP1ΔRGG fails to rescue; RGG motif necessary and sufficient to rescue PB disassembly defect. **Arginine-methylation-defective mutant (13 Arg→Ala; AMD)** also fails to rescue. **RRM1**, but not RRM2, required for stress granule assembly; deletion of either RRM did not affect Edc3 granule assembly/disassembly in the cited excerpt (pqac-00000000) | Roy R et al. *Nature Communications* (Apr 2022). DOI: https://doi.org/10.1038/s41467-022-29715-5 (pqac-00000001, pqac-00000012); Roy R et al. *bioRxiv* (Feb 2021). DOI: https://doi.org/10.1101/2021.02.23.432385 (pqac-00000000, pqac-00000002) |
| RNA-binding positional preference | CLIP analysis identified Sbp1-bound mRNAs and showed positional, not strong sequence, specificity; Sbp1-binding profiles are most similar to Dhh1 and enriched toward 5′ regions (pqac-00000008) | Sbp1 was one of four proteins (Pat1, Lsm1, Dhh1, Sbp1) profiled by CLIP. Study also noted **38%** of identified mRNA-binding proteins changed localization during stress (global context for mRNP remodeling) (pqac-00000008) | Positional preference likely linked to interaction with 5′-end-associated factor eIF4G; no specific RRM/RGG requirement quantified in the excerpt (pqac-00000008) | Mitchell SF et al. *Nature Structural & Molecular Biology* (Dec 2013). DOI: https://doi.org/10.1038/nsmb.2468 (pqac-00000008) |
| eIF4G binding | In vitro binding/pulldown assays with recombinant proteins showed direct Sbp1-eIF4G interaction; isolated Sbp1 RGG region was sufficient to bind GST-eIF4G (pqac-00000010) | Isolated **RGG motif (residues 121–180)** interacted with GST-eIF4G but not GST alone; no Kd/affinity values reported in the excerpt (pqac-00000010) | **RGG motif is required and sufficient** for eIF4G binding in the cited assays (pqac-00000010) | Rajyaguru P, She M, Parker R. *Molecular Cell* (Jan 2012). DOI: https://doi.org/10.1016/j.molcel.2011.11.026 (pqac-00000010) |
| Edc3 interaction underlying disassembly | Purified-protein pulldowns and assembly assays showed direct Sbp1-Edc3 interaction and competition with Edc3 self-association, explaining Edc3 condensate dissolution (pqac-00000000, pqac-00000002) | Sbp1 bound Edc3 **LSm-FDF** and **YjeF-N** domains, but not FDF alone, in RNA-independent conditions (RNase A present). Addition of purified Sbp1 decreased Edc3 assemblies in vitro; no binding affinity constants provided (pqac-00000000, pqac-00000002) | **RGG motif required** for dissolution of Edc3 assemblies; AMD mutant defective, implicating arginine methylation in function (pqac-00000000) | Roy R et al. *Nature Communications* (Apr 2022). DOI: https://doi.org/10.1038/s41467-022-29715-5 (supported by bioRxiv precursor DOI https://doi.org/10.1101/2021.02.23.432385) (pqac-00000000, pqac-00000002) |


*Table: This table summarizes the main experimentally supported molecular and cellular functions of S. cerevisiae Sbp1/YHL034C, including translation repression, decapping modulation, RNA-binding properties, and roles in P-body dynamics. It highlights the assays, quantitative details, and motif/domain requirements most useful for a gene-function annotation report.*