HNF1A (P20823) — review notes

Deep research: the client timed out, so the review was grounded in UniProt, GOA and cached
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was checked against this review on 2026-10-11.

• It agrees on the core annotation: HNF1A is a nuclear, sequence-specific dimeric transcriptional
  regulator, not an enzyme or a transporter, binding the inverted palindrome GTTAATNATTAAC through
  a POU-specific region plus an atypical POU homeodomain, with an N-terminal dimerization domain
  and a C-terminal transactivation region.
• It supports the DCoH/PCBD1 call: PCBD1 can stabilize the dimer, but the dimerization-domain
  protein also dimerizes without it, so the cofactor is not required for dimerization.
• It names the direct targets with the strongest human-cell support, each of which the review
  should treat as transcriptional regulation and not as HNF1A performing the downstream function:
  the pancreatic HNF4A P2 promoter (2.3 A crystal structure of the DBD-P2 complex), hepatic PCSK9
  (mutating the HNF1 element cut reporter activity to about 5% of wild type, cooperating with
  SREBP2), and renal SLC51B.
• It adds a caution the review already observes: a ChIP-seq peak assigned to its nearest gene is
  an annotation resource, not proof of regulation. Peak counts differ between preparations (739 in
  day-20 endocrine progenitors, 427 in islets, 4,791 in HepG2).

• It notes that purified protein shows phase separation and an intrinsically disordered C-terminal
  activation region in vitro, which does not establish functional condensates in human beta cells.
  Nothing in this review annotates that.

• Homeodomain/POU-like TF binding GTTAATNATTAAC as dimer PMID:12453420;
  coactivator DCoH/PCBD1 PMID:10966642.

• Renal SGLT2/glucose reabsorption PMID:11269503.
• PMID:1989880 is the TCF-1 (TCF7, HMG-box, T-cell) cloning paper PMID:1989880; the three
  HNF1A IDA annotations citing it (DNA binding, DNA-binding TF activity, positive regulation of transcription) are
  likely alias (TCF1) confusion -> UNDECIDED, reference_review MISCITED. Activities themselves are correct for HNF1A.
• HI link is weaker than for HNF4A: PMID:17407387
• insulin secretion (InterPro2GO) MARK_AS_OVER_ANNOTATED; positive regulation of insulin secretion kept NON-CORE.