DNAJC17

DNAJC17 is a nuclear speckle-localized J-domain protein (type III HSP40) that functions in pre-mRNA splicing and cell cycle control. It physically interacts with spliceosomal components, enhances splicing efficiency, and its depletion causes widespread exon skipping predominantly in cell-cycle genes, leading to G2-M arrest; the J-domain alone is sufficient to rescue both splicing and viability, while the RNA recognition motif (RRM) auto-inhibits the J-domain's allosteric activation of HSP70 ATPase activity (PMID:29773831, PMID:37961102). DNAJC17 also retains TDP-43 in the nucleus and promotes its liquid-phase behavior independently of HSP70, reducing cytoplasmic TDP-43 aggregation (PMID:40654997). Knockout of DNAJC17 in mice is embryonic lethal prior to implantation, and a conserved non-synonymous SNP in DNAJC17 modifies susceptibility to congenital hypothyroidism (PMID:20160132).

1. 2008 Medium

   The earliest functional evidence placed a DNAJC17 orthologue in the Wnt/β-catenin signaling pathway during embryogenesis, establishing that this J-protein has developmental functions beyond generic chaperone activity.

   Evidence Morpholino knockdown of Ci-FLJ10634 in Ciona intestinalis embryos phenocopied β-catenin loss, rescued by constitutively active β-catenin

   PMID:18336583

   Open questions at the time

   • Whether the Wnt pathway role is conserved in vertebrates is untested
   • Whether this function reflects a splicing role in Wnt pathway gene expression was not addressed
   • Direct biochemical interaction with β-catenin not demonstrated
2. 2010 Medium

   Mouse knockout revealed that DNAJC17 is essential for pre-implantation development and linked a conserved coding variant to congenital hypothyroidism, establishing an in vivo requirement in mammals.

   Evidence Dnajc17-null mouse embryos die before implantation; SNP analysis in thyroid bud-expressed gene identified modifier of hypothyroidism

   PMID:20160132

   Open questions at the time

   • Molecular mechanism underlying embryonic lethality not defined
   • Whether the thyroid phenotype reflects splicing defects was unknown
   • The non-synonymous SNP's effect on protein function was not biochemically tested
3. 2018 High

   The first direct mechanistic study established DNAJC17 as a nuclear speckle-resident splicing factor, resolving its molecular function: it interacts with spliceosomal components and positively regulates splicing efficiency genome-wide.

   Evidence Co-IP with splicing factors, co-localization with SC35, minigene reporter assay showing enhanced splicing upon overexpression, RNA-seq after knockdown in human cells

   PMID:29773831

   Open questions at the time

   • Which specific spliceosomal subcomplex DNAJC17 acts on was not resolved
   • Whether its J-domain chaperone activity is required for the splicing function was untested
   • No structural data on the DNAJC17–spliceosome interface
4. 2023 High

   Domain dissection revealed that the J-domain's HSP70-activating function is auto-inhibited by the RRM, and that the J-domain alone suffices for cell viability and correct splicing of cell-cycle genes at G2-M, linking splicing and cell-cycle progression through DNAJC17.

   Evidence Domain deletion/mutagenesis with viability rescue, in vitro ATPase assay, RNA-seq exon-skipping analysis in human cancer cell lines (preprint)

   PMID:37961102

   Open questions at the time

   • Whether the RRM has an independent RNA-binding function in splicing is unresolved
   • The identity of the HSP70 partner(s) activated by DNAJC17 in vivo is not established
   • How exon skipping in cell-cycle genes mechanistically leads to G2-M arrest was not dissected
5. 2025 Medium

   An HSP70-independent function was uncovered: spliceosome-associated DNAJC17 retains TDP-43 in the nucleus in a liquid phase, preventing its cytoplasmic aggregation, broadening the gene's role to proteostasis of RNA-binding proteins.

   Evidence Systematic overexpression screen, TDP-43 solubility and localization assays in human cells (preprint)

   PMID:40654997

   Open questions at the time

   • Single study, preprint; independent replication needed
   • Whether DNAJC17–TDP-43 interaction is direct or mediated by the spliceosome is unclear
   • Relevance to TDP-43 proteinopathy in ALS/FTD models not tested

• Key open questions remain: which specific HSP70 isoform(s) DNAJC17 activates in vivo, how its RRM auto-inhibition is relieved during splicing, and whether its developmental essentiality reflects splicing defects in specific gene programs.
• No structural model of DNAJC17 or its spliceosomal complex
• No in vivo conditional knockout to separate developmental from cell-cycle roles
• Relationship between Wnt pathway function in Ciona and splicing function in mammals unresolved