| Feature | UMAD1 summary | Evidence |
|---|---|---|
| Verified identity | Human **UMAD1** encodes **UBAP1-MVB12-associated domain-containing protein 1**; literature also notes it as a genuinely expressed vertebrate protein and a novel **MVB12-like ESCRT-I subunit**. This matches the UniProt-provided identity for **Homo sapiens** C9J7I0. | (pqac-00000000, pqac-00000002) |
| Alternative names / symbol context | UniProt aliases include **RPA3-AS1** and **RPA3OS**, but the protein-focused literature specifically studies the **protein-coding UMAD1** product in human cells as an ESCRT-associated factor; care is needed not to confuse the locus with antisense-RNA nomenclature. | (pqac-00000000, pqac-00000002) |
| Protein family / class | **MVB12-like, UMA-domain-containing ESCRT-I accessory subunit**. UMAD1 is incorporated into a subset of mammalian ESCRT-I heterotetramers together with TSG101, VPS28, and selected VPS37 isoforms. | (pqac-00000000, pqac-00000002, pqac-00000003) |
| Key domains | UMAD1 contains a conserved **UMA (UBAP1-MVB12-associated) domain** in its N-terminal region; UMA proteins occupy the MVB12-like position in human ESCRT-I headpieces. | (pqac-00000002, pqac-00000003, pqac-00000009) |
| Critical motif | The **VPF motif** in UMAD1’s UMA domain (**V89-P90-F91**) is essential for ESCRT-I binding. Mutation of this motif abolishes ESCRT-I association and eliminates UMAD1 rescue of cytokinesis defects. | (pqac-00000002, pqac-00000001) |
| Structural interpretation | By analogy to structural work on human ESCRT-I with MVB12A, UMA-containing proteins bind a conserved site on the **TSG101–VPS37–VPS28 headpiece**. Glover et al. further report AlphaFold2-supported conserved contacts between UMAD1’s VPF motif and **TSG101/VPS37C**. | (pqac-00000002, pqac-00000003, pqac-00000009) |
| Core binding partners | Directly or selectively associated partners include **TSG101**, **VPS28**, **VPS37C**, **VPS37B**, and **CEP55**; UMAD1 does **not** appreciably enrich ESCRT-II in the reported affinity purifications. | (pqac-00000001, pqac-00000002) |
| VPS37 subunit preference | UMAD1 shows strongest pairing with **VPS37C**, weaker but reproducible pairing with **VPS37B**, marginal association with **VPS37D**, and no clear incorporation with **VPS37A** under the tested conditions. | (pqac-00000002) |
| Relationship to other MVB12-like subunits | UMAD1 is **mutually exclusive** with other MVB12-like ESCRT-I subunits; in UMAD1-knockout cells, **UBAP1** and **MVB12A** incorporation into TSG101 complexes increases, consistent with competition for the same ESCRT-I position. | (pqac-00000001) |
| Primary molecular function | UMAD1 acts as a **cytokinesis-specialized ESCRT-I subunit/adaptor**, stabilizing the **CEP55–TSG101/ESCRT-I** interaction and thereby supporting abscission-competent ESCRT assembly at the midbody. | (pqac-00000000, pqac-00000001, pqac-00000007) |
| Primary biological process | The best-supported primary role is in **cytokinetic abscission**, the terminal step of cell division. UMAD1 depletion causes abscission delay, increased multinucleation, and reduced clonogenic growth. | (pqac-00000001, pqac-00000007) |
| Mechanistic role in abscission | UMAD1 is required not mainly for initial ESCRT-III recruitment, but for efficient **dynamic turnover/exchange of ESCRT-III subunits** at the midbody, a property needed for productive membrane scission. | (pqac-00000007, pqac-00000006) |
| Functional relationship with ALIX | UMAD1 function is **partially redundant/synergistic** with the **ALIX** arm of abscission. Co-depletion of UMAD1 and partial ALIX loss strongly worsens cytokinesis failure despite preserved CHMP4B recruitment. | (pqac-00000001, pqac-00000007, pqac-00000006) |
| Subcellular localization | UMAD1 **co-localizes with TSG101 at the midbody** during late cytokinesis and persists there until midbody resolution. Its recruitment requires **CEP55** and **TSG101/ESCRT-I** interaction. | (pqac-00000007) |
| Localization dependency | Depletion of **TSG101** or **CEP55** blocks UMAD1 recruitment to the midbody, and the VPF-mutant UMAD1 shows only background midbody localization, indicating ESCRT-I-dependent targeting downstream of CEP55. | (pqac-00000007) |
| Endosomal/lysosomal relevance | Broader ESCRT literature places UMA-containing ESCRT-I proteins in endosomal sorting. STING-trafficking datasets identify **UBAP1**-containing ESCRT-I as a key endosomal STING-degradation module and list **UMAD1** among human UMA-domain ESCRT-I options, supporting inference that UMAD1 belongs to the same ESCRT-I architectural class even though direct STING evidence is for UBAP1 rather than UMAD1. | (pqac-00000003, pqac-00000005, pqac-00000010) |
| What UMAD1 is not | UMAD1 is **not an enzyme or transporter** in the current literature; no catalytic reaction or transported substrate has been established. Its role is best described as a **scaffolding/adaptor component** that specifies ESCRT-I composition and function in membrane-remodeling pathways. | (pqac-00000000, pqac-00000002, pqac-00000003) |


*Table: This table summarizes the verified identity, domains, binding partners, localization, and best-supported functions of human UMAD1. It is useful for functional annotation because it separates directly demonstrated UMAD1 roles in cytokinetic ESCRT-I from broader ESCRT inferences about endosomal processes.*