YDJ1 encodes a type-I DnaJ/Hsp40 co-chaperone whose defining molecular
function is stimulation of the Ssa1 Hsp70 ATPase cycle [PMID:1400408, “We
report that a purified cytoplasmic Hsp70 homolog from Saccharomyces cerevisiae,
Hsp70SSA1, exhibits a weak ATPase activity, which is stimulated by a purified
eukaryotic dnaJp homolog (YDJ1p).”]. The InterPro-derived ATP
binding annotation is therefore removed: Ydj1 activates its Hsp70 partner but
has no ATP-binding/ATPase domain of its own.
All 49 unique nonredundant GOA signatures were reconciled exactly by GO term,
evidence, reference, and relation qualifier. The 62 physical GOA rows collapse
to 49 signatures because high-throughput protein binding annotations repeat
the same assertions for multiple WITH/FROM partners. All eight generic protein
binding signatures remain marked over-annotated; specific Hsp70/heat-shock
protein binding terms capture the informative partner biology.
All six IBA annotations were reviewed from their exact GOA WITH/FROM
provenance. Cytosol, cellular response to heat, protein refolding, and
obsolete unfolded protein binding use PTN001531327; ATPase activator activity
uses PTN002376157; nucleus uses PTN001180221. YDJ1 is an experimental
descendant source at PTN001531327 and PTN002376157, which is valid PAINT
grounding rather than circular evidence. The SGD:S000005021 source on the
unfolded-protein-binding and nucleus rows is APJ1, a class-A/type-I Ydj1
paralog, not SIS1. YDJ1 belongs to PTHR43888, not PTHR44298. After fetching
the correct family through the repository wrappers, the current PAINT table
retains PTN001531327, PTN001180221, and PTN002376157. Their current node-level
terms and seeds support five IBA transfers; PTN001531327 no longer carries
obsolete GO:0051082. Direct YDJ1 evidence independently supports the core
biological decisions.
GO:0051082 is obsolete in live GO, whose official obsoletion comment gives
GO:0044183 protein folding chaperone and GO:0140309 unfolded protein holdase
activity as evidence-dependent consider terms
AmiGO GO:0051082, accessed 2026-08-28.
Ydj1 directly supports both:
it suppressed thermally induced luciferase aggregation and, paired with Ssa1,
promoted productive refolding [PMID:9774392, “Ydj1:Ssa1 could promote up to
four times more luciferase folding than Sis1:Ssa1.”]. All three GO:0051082
assertions are therefore modified to both evidence-matched successor
activities, and both activities are represented in the core-function model.
The CAFA-assigned IDA chaperone-mediated protein complex assembly row has
empty WITH/FROM and cites an abstract-only human p23 paper PMID:10811660.
The abstract demonstrates p23 chaperoning of progesterone receptor but no
direct YDJ1 assay, so the row is marked over-annotated rather than treated as
MOD-curated evidence or labelled a wrong-identifier citation.
Ydj1's heat-stress quality-control role is directly supported in full text
[PMID:25344756, “We found that ubiquitylation of heat-induced substrates
requires the Hsp40 co-chaperone Ydj1 that is further associated with Rsp5 upon
heat shock.”].
ERAD and protein targeting to ER are retained as important cellular functions;
HAP1 regulation, oxygen response, starvation-linked tRNA import, nuclear
localization, and broad protein transport are retained as specialized non-core
uses of the central Hsp70 co-chaperone machinery. TRC membership is marked
over-annotated because upstream cascade participation does not establish stable
incorporation into the Get4-Get5/Mdy2 complex.
Most older supporting publications in the cache are abstract-only. Their
experimental annotations were not overruled when the abstract lacked assay
detail. Full text is locally available for PMID:19536198, PMID:23217712,
PMID:25344756, PMID:25853343, PMID:26928762, and PMID:37968396.
MISCITED/NONE for YDJ1: its