| 1999 |
HHR23A (RAD23A) is ubiquitinated in vitro and in vivo by the E3 ubiquitin ligase E6AP (UBE3A) in an E6-independent manner. HHR23A binds E6AP directly, and overexpression of dominant-negative E6AP blocks HHR23A ubiquitination. HHR23A undergoes cell-cycle-dependent degradation specifically during S phase via E6AP, and UV-induced DNA damage inhibits this degradation. |
In vitro ubiquitination assay, co-immunoprecipitation, dominant-negative E6AP overexpression, cell-cycle synchronization experiments |
The Journal of biological chemistry |
High |
10373495
|
| 2003 |
Full-length hHR23A adopts a closed conformation defined by intramolecular interactions between its N-terminal UBL domain and its two UBA domains. Binding of the proteasomal subunit S5a disrupts these interdomain interactions, causing hHR23A to adopt an open conformation. The protein contains four structured domains connected by flexible linkers. |
NMR spectroscopy, residual dipolar coupling, chemical shift perturbation analysis |
Proceedings of the National Academy of Sciences of the United States of America |
High |
14557549
|
| 2003 |
hHR23A recognizes ubiquitin through a predominantly hydrophobic surface formed by residues within helix α1 and α3 of each of its two UBA domains; these surfaces bind a region on ubiquitin that includes K48. Binding ubiquitin requires a structural change in hHR23A, and hHR23A can form a ternary complex with ubiquitin and proteasomal subunit S5a. |
NMR chemical shift perturbation, 15N NMR relaxation experiments, binding assays |
Biochemistry |
High |
14621999
|
| 2004 |
The UBL domain of HHR23A negatively regulates the interaction of its UBA domains with K48-linked polyubiquitin chains. Binding affinity for polyubiquitin increases with chain length and reaches maximum for chains of n=4–6 units, recognized by a single UBA domain. Leucine 8 of ubiquitin is an important determinant of chain recognition. |
Surface plasmon resonance, quantitative binding assays |
Journal of molecular biology |
High |
15321727
|
| 2004 |
hHR23A and hHR23B inhibit proteasomal degradation of ubiquitinated p53. siRNA depletion of hHR23A accelerates p53 degradation, while overexpression or addition of purified hHR23 proteins blocks p53 degradation in vitro. An MDM2-hHR23A complex was identified, and an MDM2 mutant with increased hHR23A binding could ubiquitinate but not degrade p53; this defect was rescued by siRNA knockdown of hHR23A, indicating MDM2 acts post-ubiquitination to counteract hHR23A inhibition. |
siRNA knockdown, in vitro proteasome degradation assay, co-immunoprecipitation, overexpression rescue experiments |
Oncogene |
High |
15064742
|
| 2000 |
Ataxin-3 interacts with both HHR23A and HHR23B via the UBL domain at the N-terminus of the HHR23 proteins. Mutant ataxin-3 recruits HHR23A to intranuclear inclusions through this interaction in 293 cells. |
Yeast two-hybrid screen, domain mapping, co-immunoprecipitation, immunofluorescence/colocalization |
Human molecular genetics |
Medium |
10915768
|
| 1997 |
HIV-1 Vpr interacts physically with HHR23A. The Vpr-binding domain maps to a C-terminal 45-amino-acid region of HHR23A (the UBA2 domain). Overexpression of HHR23A or its truncated Vpr-binding domain partially alleviates Vpr-induced G2 arrest, indicating the Vpr-HHR23A interaction is functionally relevant for cell cycle arrest. |
Yeast two-hybrid, bacterially expressed recombinant protein direct binding, indirect immunofluorescence/confocal microscopy colocalization, overexpression rescue |
Journal of virology |
Medium |
9371639
|
| 1997 |
XPC interacts in vivo with both HHR23B and HHR23A. Domain mapping shows both RAD23 homologs interact with XPC at the same highly conserved region in the C-terminal half of XPC. XPC mutants lacking this domain are deficient in both RAD23 binding and complementation of XPC cells, establishing this interaction as necessary for NER function. |
Yeast two-hybrid, domain deletion mapping, complementation assay |
Mutation research |
Medium |
9164480
|
| 2000 |
The UBA2 domain of HHR23A interacts specifically with HIV-1 Vpr. A single point mutation P333E in the hydrophobic GFP-loop of UBA2 abolishes Vpr binding without major structural changes at distal sites. High-resolution NMR structures of wild-type and mutant UBA2 confirm the hydrophobic loop as the protein-protein interaction interface. |
In vitro binding assays, site-directed mutagenesis, NMR structure determination |
Biochemistry |
High |
11087358
|
| 2004 |
The XPC-binding (XPCB) domain of hHR23A adopts a structure consisting of five amphipathic helices with hydrophobic patches on an otherwise hydrophilic surface, predicted to mediate interaction with XPC. This domain has limited sequence homology outside the Rad23 family except for sacsin. |
NMR solution structure determination |
Protein science |
Medium |
15322280
|
| 2006 |
hHR23A and hHR23B have distinct (non-redundant) interactions with proteasomes and multiubiquitinated proteins despite redundant roles in DNA repair. Threonine-79 in hHR23A contributes to its weaker proteasome binding compared to hHR23B; converting T79P (the residue in hHR23B) increases hHR23A proteasome interaction. Both proteins bind Ataxin-3 similarly but co-purify with unique proteolytic and stress-responsive factors. |
Site-directed mutagenesis, co-purification/pulldown, binding assays |
FEBS letters |
Medium |
16712842
|
| 2006 |
hHR23A interacts with hPLIC2 via UBL/UBA domain interactions, and these two ubiquitin receptor proteins associate in mammalian cells. Inhibition of the proteasome reduces the hHR23A/hPLIC2 interaction. |
NMR spectroscopy (binding surface mapping), co-immunoprecipitation in mammalian cells, proteasome inhibitor treatment |
Journal of molecular biology |
Medium |
17098253
|
| 2005 |
hHR23A knockdown reduces DNA repair activity against UVC-induced damage and prevents normal UVC-induced induction of XPC expression. Co-immunoprecipitation shows hHR23A associates with a portion of hHR23B and the majority of p53, suggesting hHR23A regulates XPC function through its association with p53. |
RNA interference, Southwestern immunoblot, host-cell reactivation assay, co-immunoprecipitation |
Biochemical and biophysical research communications |
Medium |
16105547
|
| 2010 |
The crystal structure of the UBL domain of hHR23A was determined. It shares the ubiquitin fold with overall Cα RMSD of 1.0–1.3 Å versus ubiquitin. Key residues Leu10, Ile49, and Met75 are disordered or have multiple conformations at the binding surface, suggesting conformational variability is important for interactions. Homology modelling suggests the UBL-UBA1 and UBL-UBA2 intramolecular interactions are structurally similar and mutually exclusive. |
X-ray crystallography, comparative homology modelling |
Protein engineering, design & selection |
Medium |
21047872
|
| 2013 |
HIV-1 Vpr binds hHR23A using both the XPCB and UBA2 domains simultaneously, not just UBA2 alone. NMR mapping reveals Vpr contacts substantial surfaces on both UBA2 (interacting with α2 and α3 helices of Vpr) and XPCB. Vpr binding disrupts the intramolecular UBL-UBA2 interaction in hHR23A. K48-linked di-ubiquitin binding to UBA1 does not displace Vpr, forming a ternary hHR23A·Vpr·di-Ub(K48) complex. |
NMR chemical shift perturbation/structural mapping, in vitro binding studies, mutagenesis |
The Journal of biological chemistry |
High |
24318982
|
| 2011 |
RAD23A and RAD23B participate in DNA repair and cell survival after UV irradiation with diverging functions. Long-term siRNA silencing of RAD23A in HeLa cells revealed it contributes to NER and UV survival independently from RAD23B. |
siRNA-mediated long-term gene silencing (EBV-derived plasmids), UV survival assay, DNA repair assay |
DNA repair |
Medium |
21676658
|
| 2013 |
RAD23A negatively regulates RIG-I/MDA5 innate immune signaling by interacting with TRAF2 and promoting its polyubiquitination and proteasomal degradation. Knockdown of RAD23A augments RIG-I/MDA5-mediated IFN-β and proinflammatory cytokine expression; overexpression has the opposite effect. |
siRNA knockdown, ectopic overexpression, co-immunoprecipitation, Western blotting for TRAF2 levels, reporter assays |
Biochemical and biophysical research communications |
Medium |
23357418
|
| 2016 |
E2F1 interacts directly with hHR23A proteins. This interaction stabilizes E2F1 by inhibiting its proteasomal degradation. Reciprocally, E2F1 regulates hHR23A subcellular localization, recruiting it to sites of UV-induced DNA photodamage, thereby enhancing NER in epidermal keratinocytes. |
Co-immunoprecipitation, proteasome inhibitor experiments, immunofluorescence/colocalization at DNA damage sites, UV survival/repair assays |
Oncotarget |
Medium |
27028861
|
| 2015 |
hHR23A associates with Chk1 through its UBA domains and promotes Chk1 proteasomal degradation. Knockdown of hHR23A stabilizes Chk1 protein and increases its phosphorylation at S347, resulting in S-phase accumulation. DNA damage reduces the Chk1-hHR23A interaction, releasing Chk1 to activate cell cycle checkpoints. |
siRNA knockdown, co-immunoprecipitation, domain mapping (UBA domains), flow cytometry, Western blotting |
Cellular signalling |
Medium |
26296656
|
| 2016 |
hHR23A interacts directly with Beclin 1 and LC3 (autophagy regulators). Knockdown of hHR23A increases autophagy flux as measured by EGFP-LC3 puncta, and overexpression reverses autophagy-related protein changes in knockdown cells. |
Co-immunoprecipitation, EGFP-LC3 puncta measurement, Western blotting, overexpression rescue |
Biochemical and biophysical research communications |
Low |
27613096
|
| 2021 |
Atomic resolution structure of HIV-1 Vpr in complex with the C-terminal half of hHR23A (XPCB + UBA2 domains) was determined. XPCB and UBA2 domains bind to opposite sides of Vpr's 3-helix-bundle. DCAF1 and hHR23A use overlapping binding surfaces on Vpr, revealing that Vpr independently targets hHR23A- and DCAF1-dependent pathways. |
X-ray crystallography, NMR, biochemical binding assays |
Nature communications |
High |
34824204
|
| 2010 |
hHR23A mediates the interaction of HIV-1 Vpr with the 26S proteasome (19S subunit). Depletion of hHR23A by RNAi disrupts Vpr-proteasome interaction in mammalian cells and significantly reduces HIV-1 replication in non-proliferating cells and primary macrophages. |
RNAi knockdown, co-immunoprecipitation, viral replication assay in primary macrophages |
PloS one |
Medium |
20614012
|
| 2023 |
RAD23A UBA1 and UBA2 domains each interact with Y-family DNA polymerase Pol ι at distinct, separate sites within the Pol ι catalytic domain; the UBA2 ubiquitin-binding cleft is involved, while Pol ι contacts a distinct surface on UBA1. Both UBA domain interactions are necessary for stable binding. RAD23A and RAD23B interact similarly with all four Y-family TLS polymerases (Pol ι, Pol η, Pol κ, Rev1). |
Biochemical binding assays, cell-based assays, structural assays, domain mutagenesis/deletion |
Journal of molecular biology |
Medium |
37935254
|
| 2025 |
RAD23A knockdown reduces insoluble TDP-43 levels in cells. RAD23A acts as a shuttle factor that promotes TDP-43 delivery to the proteasome; loss of RAD23A increases TDP-43 degradation and reduces aggregation. A proteomic screen identified USP13 (a deubiquitinase) as a modifier of TDP-43 aggregation, acting downstream of RAD23A. |
siRNA knockdown in inducible HEK293 cells and primary rat neurons, sarkosyl fractionation, discovery proteomics |
The Journal of neuroscience |
Medium |
41371952
|
| 2025 |
Substrate structure (folded vs. unstructured tail) determines dependency on RAD23A/B for proteasomal degradation. Well-folded ubiquitinated substrates (Ub-GFP) depend on RAD23A/B for degradation, while substrates with an unstructured tail (Ub-GFP-tail) bypass RAD23A/B. RAD23A/B interact preferentially with well-folded substrates. RAD23A/B knockdown reduces apparent ubiquitin chain lengths on substrates but only impairs degradation of the folded substrate. |
siRNA knockdown, interactome analysis (co-IP/MS), ubiquitin chain analysis, degradation assays in human cells |
Journal of biochemistry |
Medium |
40795920
|
| 2025 |
HPV16 E6 activates E6AP/UBE3A to promote ubiquitination and degradation of RAD23A. Loss of RAD23A leads to stabilization of POLQ (DNA Polymerase Theta), which RAD23A normally shuttles to the proteasome. This E6-UBE3A-RAD23A-POLQ axis promotes microhomology-mediated end joining (MMEJ) and viral genome integration. |
Overexpression, siRNA knockdown, ubiquitination assays, Western blotting, MMEJ reporter assay |
bioRxivpreprint |
Medium |
bio_10.1101_2025.11.20.689626
|
| 2025 |
The EF-hand domain of the deubiquitinase MINDY3 binds specifically to the UBL domain of RAD23A (and RAD23B) but not to other UBL domains tested. Crystal structure of the MINDY3 EF-hand:RAD23A UBL domain complex reveals the molecular basis for this specificity. MINDY3 can form a ternary complex with RAD23A/B and polyubiquitin, and the EF-hand domain mediates MINDY3 recruitment to DNA damage sites through RAD23 binding. |
Crystal structure determination, co-immunoprecipitation in cells, ternary complex assay, DNA damage recruitment assay |
bioRxivpreprint |
High |
bio_10.1101_2025.07.16.665128
|