ASDURF (ASNSD1 upstream open reading frame protein) is a 96-amino-acid microprotein translated from an upstream open reading frame (uORF) in the 5' leader of the ASNSD1 mRNA, upstream of and separate from the ASNSD1 main coding sequence. The peptide was first detected by peptidomics in K562 cells, at roughly 10-2000 copies per cell, and a tagged construct localizes to the cytoplasm. ASDURF is structurally related to beta-prefoldins. It is a subunit of the PAQosome (R2TP/prefoldin-like complex), a cytoplasmic chaperone assembly involved in the biogenesis of several multiprotein complexes. Within it, ASDURF joins PFDN2, PFDN6, UXT, URI1 and PDRG1 to form the heterohexameric prefoldin-like module. Purified ASDURF binds the prefoldin-like complex directly. ASDURF is upregulated in MYC- and MYCN-driven medulloblastoma and is required for the survival of MYC-driven medulloblastoma cells, where its loss phenocopies loss of prefoldin-like subunits. Loss of ASDURF or PFDN2 causes overlapping post-transcriptional changes in the proteome, with cell-cycle proteins prominent among them. No catalytic or chaperone activity has been shown for ASDURF itself.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | EXP PMID:23160002 Peptidomic discovery of short open reading frame-encoded pep... | ACCEPT | Summary: A FLAG-tagged ASNSD1-SEP expressed from a construct carrying the native 5' and 3' UTRs gave a cytoplasmic anti-FLAG immunofluorescence signal in HEK293T cells. Reason: Direct (if overexpression-based) localization evidence. It agrees with the cytoplasmic location of the PAQosome of which ASDURF is a subunit. Cytoplasm is broad but correct, and there is no evidence for a more specific compartment. Supporting Evidence: PMID:23160002 The uORFs ASNSD1-SEP, PHF19-SEP, DNLZ-SEP, EIF5-SEP, FRAT2-SEP, YTHDF3-SEP, CCNA2-SEP, DRAP1-SEP, TRIP6-SEP, and C7ORF47-SEP all produced cytoplasmically localized polypeptides, as detected by anti-FLAG immunofluorescence in transfected HEK293T cells |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Electronic mapping from the UniProt subcellular location (Cytoplasm), which UniProt based on PMID:23160002. Reason: Correct; duplicates the experimental annotation from PMID:23160002. Supporting Evidence: PMID:23160002 all produced cytoplasmically localized polypeptides, as detected by anti-FLAG immunofluorescence in transfected HEK293T cells |
| GO:0050821 protein stabilization | NAS PMID:31738558 Upstream ORF-Encoded ASDURF Is a Novel Prefoldin-like Subuni... | KEEP AS NON CORE | Summary: ComplexPortal annotation of the PAQosome (CPX-6145) function, applied to all twelve subunits (ASDURF, PFDN2, PFDN6, UXT, URI1, PDRG1, RPAP3, PIH1D1, RUVBL1, RUVBL2, POLR2E, DNAAF10) on the basis of PMID:31738558. Reason: The PAQosome is a chaperone for complex biogenesis, and ASDURF contributes structure to its prefoldin-like module, so a complex-level stabilization role is plausible. Neither PMID:31738558 nor PMID:38176414 shows ASDURF itself stabilizing a defined client protein. Hofman et al. do show that loss of ASDURF or PFDN2 changes protein abundance post-transcriptionally, which fits the term but does not single out stabilization. The row is NAS, inherited from the complex. It is kept as non-core, matching the call made for the same ComplexPortal row on PFDN2. Supporting Evidence: PMID:31738558 The PAQosome is an 11-subunit chaperone involved in the biogenesis of several human protein complexes. PMID:38176414 For both cell lines, we observed an overlapping proteomic signature of co-regulated proteins (Figure 5B-C), which demonstrated minimal change by RNA-seq (Figure S5C-D), confirming a post-transcriptional role for the prefoldin complex. |
| GO:1990062 RPAP3/R2TP/prefoldin-like complex | IPI PMID:31738558 Upstream ORF-Encoded ASDURF Is a Novel Prefoldin-like Subuni... | ACCEPT | Summary: Cloutier et al. identified ASDURF as the twelfth PAQosome subunit by affinity purification and mass spectrometry. It assembles with PFDN2, PFDN6, UXT, URI1 and PDRG1 into the heterohexameric prefoldin-like module. Hofman et al. independently confirmed this with co-IP/MS, endogenous PFDN6 co-IP, a direct GST pulldown, and DepMap/PRISM co-dependency profiles that cluster ASDURF with the prefoldin-like subunits and not with canonical prefoldin. Reason: The core, best-supported annotation for ASDURF, backed by two independent groups. The cached copy of PMID:31738558 is abstract-only, but the abstract states the subunit assignment explicitly and the ComplexPortal curators worked from the full text. Supporting Evidence: PMID:31738558 ASDURF, a recently discovered upstream open reading frame (uORF) in the 5' UTR of ASNSD1 mRNA, encodes the 12th subunit of the PAQosome PMID:31738558 assembles with the five known subunits of the prefoldin-like module of the PAQosome to form a heterohexameric prefoldin-like complex PMID:38176414 purified ASNSD1-uORF tagged with a Glutathione S Transferase (GST) tag showed direct interactions with the PFDL complex PMID:38176414 ASNSD1-uORF was strongly associated with the PFDL but not the PFD complex |
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Download this section (compressed HTML)Q: Does ASDURF replace a canonical beta-prefoldin position in the prefoldin-like hexamer (making it obligatory for PAQosome assembly), or is it a substoichiometric or exchangeable subunit?
Q: Which PAQosome client complexes (for example RNA polymerase II, snoRNPs, PIKK complexes) depend specifically on ASDURF, and does that explain the post-transcriptional cell-cycle proteome signature seen after its loss?
Q: Does translation of the ASDURF uORF also regulate translation of the downstream ASNSD1 coding sequence in cis, independent of the peptide's trans function?
Experiment: Assemble the prefoldin-like module from recombinant subunits with and without ASDURF, and test assembly and client binding (for example RPB5/POLR2E or unfolded model substrates). This would show whether ASDURF is structurally required and whether the module has holdase activity.
Experiment: Delete ASDURF without changing the ASNSD1 coding sequence (start-codon mutation in the endogenous locus). Then measure PAQosome integrity and the assembly of known client complexes by quantitative proteomics.
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