| Functional role/Process | Mechanism & key partners | Subcellular location | Evidence type (assay/structure) | Key quantitative/structural details | Primary sources (with year, journal, URL) |
|---|---|---|---|---|---|
| Ribosome collision sensor/adaptor in ribosome-associated quality control | EDF1 is recruited to collided ribosomes independently of ZNF598 but promotes downstream recruitment of GIGYF2/EIF4E2 (4EHP) to repress new initiation on defective mRNAs; facilitates efficient ZNF598-dependent eS10/uS10 ubiquitylation and contributes to collision-triggered p38/ZAKα signaling; recruitment depends on RACK1. (pqac-00000001, pqac-00000017, pqac-00000018, pqac-00000021) | Predominantly cytoplasmic; accumulates on polysomes/collided ribosomes during translational distress. (pqac-00000001, pqac-00000002) | Sucrose-gradient polysome fractionation, TMT proteomics, KO/depletion, immunoblotting, cryo-EM. (pqac-00000001, pqac-00000006) | Human EDF1 is ~16.4 kDa; EDF1 loss caused a modest ~10–20% decrease in ZNF598 recruitment; cryo-EM resolved EDF1 bound to non-rotated human 80S at 2.9 Å near the 40S mRNA entry channel. (pqac-00000001, pqac-00000006) | Sinha et al. 2020, *eLife*, https://doi.org/10.7554/eLife.58828 (pqac-00000001, pqac-00000006) |
| Transcriptional coactivator bridging basal and sequence-specific transcription factors | hMBF1α is identical to EDF1 and binds TBP plus gene-specific activators including Ad4BP/SF-1 and ATF1/bZIP-family factors (ATF1, CREB/CREBP, c-Jun, c-Fos); enhances DNA binding of some partners and mediates Ad4BP/SF-1- and ATF1-dependent transcription. Nuclear accumulation is induced by coexpression with nuclear Ad4BP/SF-1. (pqac-00000003, pqac-00000011, pqac-00000012, pqac-00000013, pqac-00000014, pqac-00000016) | Cytoplasmic when expressed alone; nuclear enrichment upon interaction with nuclear partners such as Ad4BP/SF-1. (pqac-00000004, pqac-00000008, pqac-00000011) | GST pull-downs, co-immunoprecipitation, EMSA/DNA-binding assays, transient reporter assays, immunofluorescence. (pqac-00000003, pqac-00000004, pqac-00000011, pqac-00000014) | hMBF1a/b increased Ad4BP/SF-1-dependent transcription by ~3.5–4-fold; central region aa 69–108 required for interaction; basic-region contacts mapped on Ad4BP/SF-1 and bZIP factors. (pqac-00000014) | Kabe et al. 1999, *J Biol Chem*, https://doi.org/10.1074/jbc.274.48.34196 (pqac-00000003, pqac-00000014) |
| CaM-binding signaling-responsive shuttling factor | EDF1 binds calmodulin (CaM) in vitro and in vivo; PKC phosphorylation disrupts CaM binding, and PKA phosphorylation modulates EDF1/CaM interaction and correlates with signaling-dependent nuclear accumulation; native and PKC-phosphorylated EDF1 can still interact with TBP, supporting a cytosol-to-nucleus switch between CaM-associated and coactivator states. (pqac-00000009, pqac-00000010) | Basal distribution in cytosol and nucleus; TPA and forskolin increase nuclear-associated EDF1. (pqac-00000009, pqac-00000010) | In vitro/in vivo phosphorylation assays, CaM-binding assays, co-immunoprecipitation, localization studies in HUVEC/COS cells. (pqac-00000009, pqac-00000010) | Thr91→Asp phosphomimetic abolished CaM binding; PKC and PKA both regulate EDF1 localization/function; TPA stimulated EDF1 phosphorylation and nuclear translocation. (pqac-00000009, pqac-00000010) | Mariotti et al. 2000, *J Biol Chem*, https://doi.org/10.1074/jbc.M001928200; Mariotti et al. 2004, *Cell Mol Life Sci*, https://doi.org/10.1007/s00018-004-4016-0 (pqac-00000009, pqac-00000010) |
| Collision-coupled integrated stress response (ISR) activator / frameshift suppressor | Recent work argues EDF1/Mbf1 acts primarily at collided ribosomes, not as a direct nuclear coactivator in ISR; recruitment to collided ribosomes promotes upstream GCN2 pathway activation and eIF2α phosphorylation (shown mechanistically in yeast, inferred conserved for human EDF1), while Mbf1/EDF1 contacts rRNA, ribosomal proteins, and mRNA to prevent frameshifting. (pqac-00000007, pqac-00000020) | Cytoplasmic; 2024 study reports human EDF1 “exclusively resides in the cytoplasm,” with no stress-induced relocalization detected. (pqac-00000007, pqac-00000020) | Subcellular fractionation, promoter occupancy/ChIP analyses, collision/ISR assays, comparative mechanistic inference with structural data. (pqac-00000007, pqac-00000020) | Yeast/human Mbf1-EDF1 present at concentrations orders of magnitude above typical transcription factors; supports stoichiometric ribosome-associated role rather than classical limiting nuclear coactivator role. (pqac-00000007) | Kim et al. 2024, *Molecular Cell*, https://doi.org/10.1016/j.molcel.2024.10.029 (pqac-00000007, pqac-00000020) |
| Structural basis of EDF1 domain function | EDF1 contains an N-terminal MBF1 domain and C-terminal Cro/C1-type HTH domain; on collided ribosomes, the HTH domain sits between h16 and h33, while the N-terminal helix contacts h16/uS4/eS30; EDF1 also engages h18 and uS3, consistent with UniProt domain annotation and a direct ribosome-binding mechanism. (pqac-00000002, pqac-00000006, pqac-00000023) | 40S subunit mRNA entry channel on stalled/collided 80S ribosomes. (pqac-00000006, pqac-00000023) | Cryo-EM structural modeling. (pqac-00000006, pqac-00000023) | Near-complete human model built for Ser24–Arg133; conserved GQNKQ and KKW motifs contribute to rRNA/mRNA-path contacts; interface includes uS3, uS4, eS30 and rRNA helices h16, h18, h33. (pqac-00000006, pqac-00000023) | Sinha et al. 2020, *eLife*, https://doi.org/10.7554/eLife.58828 (pqac-00000002, pqac-00000006, pqac-00000023) |


*Table: This table consolidates the main experimentally supported functions of human EDF1/MBF1 (UniProt O60869), emphasizing both the classical transcriptional coactivator literature and the newer ribosome-collision quality-control model. It is useful for reconciling EDF1’s localization, partners, mechanisms, and strongest primary evidence.*