NKX2-5 (human, P52952) curation notes

Provenance note

Automated deep research could not be run for this gene (falcon provider returned HTTP 402,
OpenAI provider returned HTTP 401). No *-deep-research-<provider>.md file was created.
These notes were assembled manually from the cached publications in publications/
(several are abstract-only; full_text_available checked per paper), the UniProt record
(NKX2-5-uniprot.txt) and PubMed searches used to locate three additional key mouse papers
(PMID:7628699, PMID:17350578, PMID:15085192), which were already cached.

Identity and structure

• NK-2 class homeodomain transcription factor; vertebrate ortholog of Drosophila tinman.
  PMID:8900537
  PMID:8900537
• Homeodomain binds the NKE (TNAAGTG; TAAG core) element. Crystal structure of the HD on the
  NPPA/ANF -242 element: PMID:22849347
  and PMID:22849347.
  (Note: argues against a DNA-independent homodimer interface in the HD; UniProt still states "Homodimer".)
• Nuclear localization signal at the N-terminus of the homeodomain; CK2 phosphorylation of the HD
  (Ser163) increases DNA binding. PMID:9858576
• C-terminal autorepressive domain; GATA4 binding to it unmasks activation.
  PMID:9312027
• SUMOylated at K51 (PIAS1/PIASx/PIASy), which enhances activity.
  PMID:18579533

Molecular function: sequence-specific RNA Pol II TF (activator > repressor)

• Activates NPPA/ANF through the NKE2 element. PMID:10075728
• Context-dependent repression: PMID:10075728
• Direct targets in human fetal cardiomyocytes: activates GATA4, represses CTNNB1 (beta-catenin)
  through promoter NKEs. PMID:19479054
• Activates miR-143/145 enhancer together with SRF/MYOCD. PMID:19578358
• Activates COL3A1 in pulmonary artery endothelial cells with NEDD9 (non-cardiac context).
  PMID:29899023
• Ectopically expressed in T-ALL, activating MEF2C. PMID:18079734
• HT-SELEX (methyl-SELEX) profiling of human TFs includes NKX2-5 (PMID:28473536; NKX2-5 only in supplementary data).

Partners (combinatorial cardiac TF code)

• GATA4: mutual cofactors, synergistic activation of ANF. PMID:9312027
• TBX5: binds Nppa in tandem; synergy; HD of NKX2-5 required. PMID:11431700
  Ternary structure: PMID:26926761
  Holt-Oram TBX5 mutants lose the interaction: PMID:12499378
• Coactivators: Cal/FBLIM1 PMID:14757752; CAMTA2 PMID:16678093.
• MYOCD binds NKX2-5 but without functional synergy at ACTG2 PMID:19797053.
• HuRI Y2H hits (SHOX, TRIP10, KRTAP8-1, RBPMS; PMID:32296183) - no functional follow-up.

Biological roles

Heart (core)

• Mouse null: heart tube forms, but looping fails and ventricular MLC2v is absent.
  PMID:7628699
  PMID:7628699
• Second heart field: PMID:17350578
• Conduction system: dosage-dependent; AV node primordium absent in nulls.
  PMID:15085192
  PMID:15109497
• Adult myocyte survival: PMID:11889119
• Cardiomyocyte differentiation with TBX5 in P19CL6 cells (PMID:11431700).

Human disease (heterozygous, dosage-sensitive)

• ASD with AV block: PMID:9651244
• Broader CHD spectrum: PMID:10587520; TOF/DORV, Ebstein.
• Disease mutants lose DNA binding/transactivation: PMID:10948187

Non-cardiac

• Spleen: PMID:22560297; human isolated congenital asplenia P236H.
• Thyroid: PMID:16418214
• Overexpression in C2C12 myoblasts blocks myotube formation and induces neuron-like cells (PMID:15653675) - ectopic, not physiological.

Curation judgements (summary)

• Core: GO:0000981 / GO:0000978 / GO:0045944 / nucleus-chromatin; GATA4/TBX5 binding as
  GO:0061629; heart looping, cardiac muscle cell differentiation, AV node/conduction system
  development, atrial/ventricular septum morphogenesis.
• Non-core: spleen, thyroid, pharyngeal, adult heart maintenance, anti-apoptotic, Wnt repression.
• Over-annotated: sodium ion transport, heart contraction, cardiac muscle contraction,
  hemopoiesis, vasculogenesis, neuron differentiation, myotube differentiation, cytoplasm,
  homodimerization.
• protein binding (GO:0005515): GATA4/TBX5 -> MODIFY to GO:0061629; Cal/FBLIM1 -> GO:0001223;
  PIAS1, MYOCD, NEDD9 and HuRI Y2H rows -> REMOVE (uninformative).