title: Regulation of the Drosophila bHLH-PAS protein Sima by hypoxia: functional evidence for homology with mammalian HIF-1 alpha.
abstract: Hypoxia inducible factor-1 (HIF-1) is a heterodimeric complex of two basic-helix-loop-helix proteins of the PAS family which is critical for oxygen-dependent expression of many mammalian genes. Regulation is mediated by the alpha subunit (HIF-1 alpha) and sequences from HIF-1 alpha can confer hypoxia-inducible activity on a Ga14 fusion protein. To analyse conservation of this system of gene regulation between Drosophila and mammalian cells we constructed Ga14 fusions with a series of Drosophila basic-helix-loop-helix PAS (bHLH-PAS) proteins and tested for hypoxia inducibility in transfected Hep3B cells. We found that Ga14 functions with Similar (Sima) but not other Drosophila bHLH-PAS proteins showed inducible activity following exposure to stimuli which classically activate mammalian HIF-1:hypoxia, cobaltous ions, and desferrioxamine. We also found that Sima protein accumulated in Drosophila SL2 cells following hypoxia. Together these findings indicate the existence of functional homologies between Sima and HIF-1 alpha, and that conservation is such as to enable Sima to interact with the hypoxia signal transduction system in mammalian cells.
authors.affiliation: Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, United Kingdom.
authors.forename: N C
authors.initials: NC
authors.lastname: Bacon
authors.forename: P
authors.initials: P
authors.lastname: Wappner
authors.forename: J F
authors.initials: JF
authors.lastname: O'Rourke
authors.forename: S M
authors.initials: SM
authors.lastname: Bartlett
authors.forename: B
authors.initials: B
authors.lastname: Shilo
authors.forename: C W
authors.initials: CW
authors.lastname: Pugh
authors.forename: P J
authors.initials: PJ
authors.lastname: Ratcliffe
mesh_terms: D000818:Animals; D015687:Cell Hypoxia / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D017344:Genes, Insect; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013045:Species Specificity; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019476:Insect Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C100429:Sima protein, Drosophila; D014157:Transcription Factors; D010100:Oxygen