module: dmel_hif_complex
title: Hypoxia-inducible factor (Sima-Tgo) in Drosophila melanogaster
label: Hypoxia-inducible factor
module_type: PROTEIN_COMPLEX
description: >-
  Hypoxia-inducible factor is a bHLH-PAS heterodimer that activates
  transcription when oxygen is low. The oxygen-regulated alpha subunit Sima
  (similar) is hydroxylated by the prolyl hydroxylase Fatiga in normoxia and
  degraded; in hypoxia it accumulates, enters the nucleus and dimerizes with the
  constitutive beta subunit Tango (tgo), the Drosophila ARNT homolog, to bind
  hypoxia response elements. Sima-Tgo drives hypoxia-induced gene expression,
  including tracheal branching responses, and Sima also has roles in growth
  control under normoxia.
summary: >-
  Sima-Tgo bHLH-PAS heterodimer that activates gene expression in hypoxia.
concepts:
  - {id: GO:0090575, label: RNA polymerase II transcription regulator complex}
cellular_components:
  - {id: GO:0005634, label: nucleus}
group: HIF
roles:
  sima: oxygen-regulated alpha subunit
  tgo: constitutive beta subunit (ARNT)
unit_functions:
  sima: {id: GO:0000981, label: "DNA-binding transcription factor activity, RNA polymerase II-specific"}
  tgo: {id: GO:0000981, label: "DNA-binding transcription factor activity, RNA polymerase II-specific"}
notes: >-
  GO has no specific cellular-component term for the HIF heterodimer, so the
  general RNA polymerase II transcription regulator complex term is used. Tgo is
  also the common partner of other bHLH-PAS proteins (for example single-minded,
  trachealess, spineless); only its HIF role is modelled here. The oxygen
  sensor Fatiga (Hph) and the VHL ubiquitin ligase are regulators and are not
  parts.