{"uniprot":"P0CG21","gene":"NHLRC4","name":"NHL-repeat-containing protein 4","organism":"Homo sapiens (Human)","status":"dark","length":123,"sequence":"MLGLEGPCWVGPGPDGGLAVSEEFGDVRLFGSARQPLGSLGGWTGHTFGCPAGICSNSEGNVIVADEQRRQVTLFPRAGPPICLVSEGLGQPLGVACAPQGQLLVADAKDNSIKVYQGLKELA","function_summary":"A nucleocytoplasmic adaptor that uses an NHL-repeat beta-propeller scaffold to organize RNA–protein assemblies controlling post-transcriptional gene expression. By concentrating binding interfaces rather than catalytic motifs, it assembles and remodels ribonucleoprotein complexes that repress translation in the cytosol while also influencing pre-mRNA splicing and nuclear export within the nucleoplasm. Its soluble architecture supports shuttling between these compartments to couple nuclear RNA processing with cytoplasmic translational control.","plain_language":"NHLRC4 has barely been studied. The model's best guess: A nucleocytoplasmic adaptor that uses an NHL-repeat beta-propeller scaffold to organize RNA–protein assemblies controlling post-transcriptional gene expression. By concentrating binding interfaces rather than catalytic motifs, it assembles and remodels ribonucleoprotein complexes that repress translation in the cytosol while also influencing pre-mRNA splicing and nuclear export within the nucleoplasm.","uniprot_summary":"May be involved in gene expression mechanisms, such as pre-mRNA splicing and nuclear export.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0017148","label":"negative regulation of translation"}],"cellular_component":[{"id":"GO:0005829","label":"cytosol"},{"id":"GO:0005654","label":"nucleoplasm"}]},"interpro":[{"id":"IPR011042","name":"Six-bladed beta-propeller, TolB-like","type":"homologous_superfamily","start":5,"end":122},{"id":"IPR001258","name":"NHL repeat","type":"repeat","start":48,"end":67},{"id":"IPR001258","name":"NHL repeat","type":"repeat","start":89,"end":119}],"reasoning":"I begin with the InterPro architecture. The N-terminal two-thirds of the polypeptide (residues 5–122) is covered by IPR011042, a six-bladed beta-propeller, TolB-like homologous superfamily. This fold creates a radially arranged, solvent-exposed platform that typically mediates multivalent macromolecular recognition rather than catalysis. Within this propeller scaffold lie two tandem NHL repeats: IPR001258 (NHL repeat, residues 48–67) and IPR001258 (NHL repeat, residues 89–119). NHL repeats are characteristic blades or segments of beta-propellers that tune sequence-specific binding to RNA and proteins. The ordered arrangement—an NHL-repeat–decorated TolB-like propeller—causes high-affinity, avidity-driven interactions with RNA–protein assemblies and soluble factors, favoring a non-enzymatic adaptor role. This architecture directly supports a molecular function centered on multivalent macromolecular contacts, consistent with GO:0005515 protein binding.\n\nFrom this binding-centric core, I infer how the protein regulates gene expression post-transcriptionally. NHL-propeller scaffolds frequently dock onto translational machinery and RNA granules. Such docking can repress ribosome engagement or promote assembly of inhibitory ribonucleoprotein complexes, providing a mechanistic route to GO:0017148 negative regulation of translation. The same scaffold can also stabilize or remodel ribonucleoprotein assemblies that influence mRNA maturation and export, explaining how it may modulate pre-mRNA splicing and nuclear export while simultaneously tuning cytosolic translation.\n\nCellular localization follows from this dual operational landscape. The soluble beta-propeller lacks transmembrane segments and secretory signals, favoring a cytosolic and nucleoplasmic distribution. Its role in translational repression and mRNP remodeling anchors it in the cytosol (GO:0005829 cytosol), while its influence on splicing and mRNA processing necessitates nucleoplasmic residency (GO:0005654 nucleoplasm). This nucleocytoplasmic shuttling enables the protein to couple nuclear RNA processing with cytoplasmic utilization or repression of mRNA.\n\nMechanistically, I hypothesize that the NHL-repeat beta-propeller nucleates transient assemblies with RNA-binding proteins and translation factors to gate ribosome access and mRNP fate. In the nucleus, it likely associates with spliceosomal adaptors and export receptors to shape pre-mRNA processing and handoff. In the cytosol, it may bind cap-binding or initiation complexes to dampen initiation, and engage granule-associated adaptors to sequester target transcripts. Candidate partners include initiation factors (eIF4E/eIF4G), poly(A)-binding proteins, and granule organizers such as LSM and DDX-family helicases. Together, these interactions would allow the propeller scaffold to coordinate translational repression with broader RNA maturation and export pathways.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-P0CG21.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/P0CG21"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/P0CG21/entry","atlas":"/p/P0CG21"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}