DNAJC17

DNAJC17 is a pan-essential HSP40/J-domain co-chaperone that links the HSP70 chaperone system to nuclear pre-mRNA splicing (PMID:37961102, PMID:29773831). It localizes to nuclear speckles and physically associates with spliceosomal/splicing machinery components, where it supports splicing efficiency (PMID:29773831). Its J-domain allosterically activates ATP hydrolysis by HSP70, while its RNA recognition motif (RRM) imposes an auto-inhibitory constraint on this activation; the J-domain alone is both required and sufficient to rescue viability, splicing, and G2-M progression after loss of endogenous protein, whereas the RRM and C-terminal alpha helix are dispensable (PMID:37961102, PMID:42156896). Loss of DNAJC17 causes exon skipping concentrated in cell-cycle genes rather than broad changes in mRNA abundance, deranging G2-M progression and producing cell lethality (PMID:42156896). The protein additionally retains the RNA-binding protein TDP-43 in the nucleus and promotes its liquid-phase behavior, reducing TDP-43 aggregate burden under proteotoxic stress through an HSP70-independent route (PMID:40654997). In mouse, Dnajc17 is essential for early development, with knockout embryos dying before implantation (PMID:20160132).

1. 2008 Medium

   Established the first developmental function for a DNAJC17 orthologue by placing it within canonical Wnt/beta-catenin signaling during early embryogenesis, addressing whether this J-protein had a defined pathway role.

   Evidence Morpholino knockdown with beta-catenin epistasis/rescue and downstream target analysis in Ciona intestinalis embryos

   PMID:18336583

   Open questions at the time

   • Invertebrate orthologue context; relevance to vertebrate/human DNAJC17 unconfirmed
   • Molecular mechanism by which the J-protein acts on Wnt signaling not defined
   • No biochemical link to HSP70 or splicing established here
2. 2010 Medium

   Showed that mammalian Dnajc17 is essential for early development and a genetic modifier of thyroid phenotypes, establishing organismal requirement before any molecular mechanism was known.

   Evidence Knockout mouse (pre-implantation lethality), thyroid bud expression profiling, and SNP-based modifier mapping of congenital hypothyroidism

   PMID:20160132

   Open questions at the time

   • Lethality precludes definition of tissue-specific function
   • Mechanism connecting Dnajc17 to thyroid gene-dosage phenotypes unknown
   • No molecular activity assigned
3. 2017 Low

   Tested whether DNAJC17 coding mutations cause human thyroid dysgenesis, addressing the clinical relevance of the mouse modifier findings.

   Evidence HRM and direct sequencing of DNAJC17 coding region in 89 thyroid dysgenesis patients versus controls

   PMID:29159607

   Open questions at the time

   • Negative/null association in a single small cohort; does not exclude rare or regulatory variants
   • No functional testing of the identified variants
   • Cohort size limits statistical power
4. 2018 High

   Defined a molecular function for DNAJC17 by localizing it to nuclear speckles and tying it to the splicing machinery, the first direct evidence for a role in pre-mRNA splicing.

   Evidence Co-IP, in vivo co-localization with SC35, minigene splicing reporter, and RNAseq upon knockdown in human cells

   PMID:29773831

   Open questions at the time

   • Specific spliceosomal subcomplex/contacts not resolved
   • Mechanistic link between speckle localization and splicing outcomes undefined
   • No connection to chaperone activity made at this stage
5. 2023 High

   Unified the chaperone and splicing roles by showing DNAJC17 is pan-essential, that its J-domain activates HSP70 ATPase activity, that the RRM auto-inhibits this activity, and that the J-domain alone suffices for viability.

   Evidence JDP-library genetic screen, domain-deletion/rescue, in vitro HSP70 ATPase assay, and RNAseq exon-skipping analysis in human cancer cell lines (preprint)

   PMID:37961102

   Open questions at the time

   • Identity of client proteins handed to HSP70 not determined
   • How J-domain/HSP70 activity mechanistically promotes correct splicing unresolved
   • Structural basis of RRM auto-inhibition not defined
6. 2025 Medium

   Extended DNAJC17 function to proteostasis of an aggregation-prone RNA-binding protein, showing it retains TDP-43 in the nucleus and suppresses its aggregation independently of HSP70.

   Evidence Systematic overexpression screen of the HSP70 network, TDP-43 aggregation/localization/phase-behavior imaging, and viability assays in human cells (preprint)

   PMID:40654997

   Open questions at the time

   • Single-lab preprint; reciprocal/independent validation pending
   • Molecular basis of HSP70-independent TDP-43 retention undefined
   • Relationship to the J-domain/RRM mechanism not established
7. 2026 High

   Confirmed and extended the domain-function model in peer review, establishing that the J-domain is required and sufficient to rescue viability, splicing, and G2-M progression while the RRM and C-terminal helix are dispensable.

   Evidence Genetic screen, domain-deletion rescue, in vitro HSP70 ATPase assay, RNAseq exon-skipping, and viability assays in human cancer cell lines

   PMID:42156896

   Open questions at the time

   • Functional role of the auto-inhibitory RRM in vivo unclear given its dispensability for rescue
   • Direct HSP70 clients during splicing not identified
   • Mechanism coupling chaperone activity to exon inclusion unresolved

• How HSP70 chaperone activity is mechanistically coupled to correct spliceosome function, and what client proteins DNAJC17 delivers, remain undefined.
• No HSP70 clients of DNAJC17 identified
• Structural basis of RRM auto-inhibition and J-domain/HSP70 engagement not solved
• Reconciliation of essential splicing role with HSP70-independent TDP-43 retention not established