GRWD1

GRWD1 is a WD40-repeat protein that couples chromatin regulation, ribosome biogenesis, and p53 control to influence DNA replication licensing and cell proliferation (PMID:25990725, PMID:15885502). At chromatin, GRWD1 binds histones and disassembles nucleosomes in an ATP-independent manner, evicting H2A-H2B dimers to form hexasomes through its N-terminal acidic domain; this activity maintains chromatin openness at replication origins and facilitates MCM helicase loading during G1 in a CDC6- and Cdt1-dependent manner (PMID:25990725, PMID:27552915). GRWD1 localizes to nucleoli and is released to the nucleoplasm under nucleolar stress, where it negatively regulates the tumor suppressor p53 by multiple routes: it competes with MDM2 for binding to RPL11, relieving RPL11-mediated suppression of MDM2 ubiquitin ligase activity (PMID:27856536); it cooperates with the E3 ligase EDD/UBR5 to drive ubiquitylation and proteasomal degradation of RPL23, removing another MDM2 inhibitor and promoting anchorage-independent growth (PMID:29991511); and it directly binds the p53 DNA-binding domain to suppress transcription from p53 target promoters including p21 and MDM2 (PMID:31545368). GRWD1 also associates with the H3K4 methyltransferase machinery via WDR5 and MLL2 to maintain H3K4me3 at specific loci (PMID:34933446), and it participates in HSV-1 nuclear egress through interaction with the viral kinase US3 and promotion of Lamin A/C degradation (PMID:41995456). Its broader role in chromosome segregation and ribosome biogenesis is supported by genetic and biochemical evidence from the yeast ortholog RRB1 and human knockdown phenotypes (PMID:15467761, PMID:15885502).

1. 2004 Medium

   Established the first functional link between GRWD1 and the coordination of ribosome biogenesis with genome maintenance, situating the protein at the interface of these processes.

   Evidence Yeast RRB1 interaction assays (Yph1, RPL3, ERB1, ORC6) and human GRWD1 knockdown mitosis phenotyping

   PMID:15467761

   Open questions at the time

   • Did not define the biochemical activity of GRWD1 on chromatin or replication origins
   • Mitotic defects not mechanistically connected to a specific molecular substrate
2. 2005 Medium

   Showed GRWD1 physically co-sediments with preribosomal complexes and is required for proliferation and protein synthesis, supporting a role in ribosome biogenesis.

   Evidence Nuclear fractionation/cosedimentation with Bop1, siRNA knockdown, metabolic labeling of protein synthesis

   PMID:15885502

   Open questions at the time

   • Co-sedimentation does not establish direct binding to ribosomal subunits
   • Did not separate ribosome biogenesis effects from replication or p53 roles
3. 2015 High

   Defined GRWD1 as a replication-licensing factor that binds origins in G1 and promotes MCM loading by regulating chromatin openness, answering how it influences DNA replication.

   Evidence ChIP/ChIP-seq at origins, FAIRE-seq, histone-binding assay, siRNA knockdown in human cells

   PMID:25990725

   Open questions at the time

   • Mechanism of how histone binding produces chromatin openness not yet resolved at this stage
   • Genome-wide origin specificity determinants unknown
4. 2016 High

   Determined the biochemical basis of GRWD1's chromatin activity, showing it is an ATP-independent nucleosome disassembly factor whose acidic domain evicts H2A-H2B.

   Evidence In vitro reconstituted mononucleosome disassembly with recombinant histones, deletion mutagenesis, FAIRE-qPCR

   PMID:27552915

   Open questions at the time

   • Does not explain how disassembly is targeted to specific origins in vivo
   • Fate of evicted H2A-H2B and reassembly partners undefined
5. 2016 High

   Connected GRWD1 to p53 control via the ribosomal stress pathway, showing it competes with MDM2 for RPL11 to reduce p53 stability and responds to nucleolar stress.

   Evidence Reciprocal Co-IP, MDM2 ubiquitin ligase assay, domain mapping, subcellular fractionation/immunofluorescence

   PMID:27856536

   Open questions at the time

   • Did not address whether GRWD1 acts on p53 through additional routes
   • In vivo tumor relevance not tested
6. 2018 High

   Identified a second p53-suppressing mechanism in which GRWD1 recruits EDD/UBR5 to degrade RPL23, linking GRWD1 to oncogenic growth.

   Evidence MS interactome, reciprocal Co-IP, ubiquitylation assay, MG132 rescue, colony formation assay

   PMID:29991511

   Open questions at the time

   • Relative contribution of RPL23 versus RPL11 routes to p53 control unquantified
   • Structural basis of GRWD1-EDD-RPL23 assembly unknown
7. 2020 Medium

   Demonstrated a third, direct mode of p53 inhibition by GRWD1 binding the p53 DNA-binding domain and suppressing target promoters.

   Evidence Co-IP with domain mapping, ChIP at p21/MDM2 promoters, reporter assays, siRNA knockdown

   PMID:31545368

   Open questions at the time

   • Single-lab study without reciprocal structural validation
   • Interplay between direct binding and ribosomal-protein-mediated routes not resolved
8. 2020 Medium

   Placed GRWD1 downstream of a lncRNA regulator, showing PiHL enhances GRWD1-RPL11 complex formation to suppress p53 in colorectal cancer.

   Evidence Co-IP, siRNA/overexpression, in vitro and in vivo tumor models

   PMID:31903119

   Open questions at the time

   • How PiHL physically promotes complex formation not mechanistically defined
   • Generality beyond colorectal cancer untested
9. 2021 Medium

   Expanded GRWD1's chromatin role beyond replication, showing it associates with WDR5/MLL2 to maintain the H3K4me3 active mark at specific loci.

   Evidence CRISPR screen, Co-IP of GRWD1-WDR5-MLL2, H3K4me3 ChIP-seq, RNA-seq, tumor formation assay

   PMID:34933446

   Open questions at the time

   • Stoichiometry and architecture of the GRWD1-WDR5-MLL2 complex unknown
   • Relationship between methyltransferase role and nucleosome disassembly activity unresolved
10. 2026 Medium

    Revealed a host-pathogen role in which GRWD1 facilitates HSV-1 nuclear egress by degrading Lamin A/C in a US3-dependent manner.

    Evidence siRNA knockdown, Co-IP (US3, Lamin A), immunofluorescence colocalization with UL34, Lamin A/C degradation blots, US3-deficient infection, viral replication assay

    PMID:41995456

    Open questions at the time

    • Mechanism by which GRWD1 promotes Lamin A/C proteasomal degradation undefined
    • Whether nuclear lamina disruption is direct or via recruited ligases unknown
11. 2025 Low

    Linked GRWD1 to disease through abnormal interaction with cardiomyopathy-associated RPL3L variants, proposing a gain-of-toxicity ribosome biogenesis defect.

    Evidence Binding affinity assay, nuclear rRNA localization, ribosome biogenesis assays, patient variant analysis (preprint)

    PMID:bio_10.1101_2025.01.02.630345

    Open questions at the time

    • Preprint with binding affinity data lacking mutagenesis or reconstitution validation
    • Causal role of GRWD1 in the disease phenotype not established
12. 2025 Low

    Positioned GRWD1 downstream of IL-6/STAT3 signaling driving p53 degradation and aerobic glycolysis in colorectal cancer.

    Evidence IL-6 stimulation, STAT3 modulation, western blot, AOM/DSS mouse model, siRNA knockdown

    PMID:41022893

    Open questions at the time

    • Pathway placement based on western blot without direct binding or reconstitution
    • Mechanism linking GRWD1 to GLUT1 upregulation undefined

• How GRWD1's distinct activities — origin licensing, nucleosome disassembly, p53 suppression, H3K4me3 maintenance, ribosome biogenesis — are coordinated and regulated within a single protein remains unresolved.
• No structural model integrating the WD40 repeats and N-terminal acidic domain functions
• Determinants of nucleolar versus chromatin partitioning unknown
• Whether the multiple p53-suppressing routes operate simultaneously or context-specifically is undefined