title: Oxygen sensing in Drosophila: multiple isoforms of the prolyl hydroxylase fatiga have different capacity to regulate HIFalpha/Sima.
abstract: BACKGROUND
  The Hypoxia Inducible Factor (HIF) mediates cellular adaptations to low oxygen. Prolyl-4-hydroxylases are oxygen sensors that hydroxylate the HIF alpha-subunit, promoting its proteasomal degradation in normoxia. Three HIF-prolyl hydroxylases, encoded by independent genes, PHD1, PHD2, and PHD3, occur in mammals. PHD2, the longest PHD isoform includes a MYND domain, whose biochemical function is unclear. PHD2 and PHD3 genes are induced in hypoxia to shut down HIF dependent transcription upon reoxygenation, while expression of PHD1 is oxygen-independent. The physiologic significance of the diversity of the PHD oxygen sensors is intriguing.
  
  
  RESULTS
  We have analyzed the Drosophila PHD locus, fatiga, which encodes 3 isoforms, FgaA, FgaB and FgaC that are originated through a combination of alternative initiation of transcription and alternative splicing. FgaA includes a MYND domain and is homologous to PHD2, while FgaB and FgaC are shorter isoforms most similar to PHD3. Through a combination of genetic experiments in vivo and molecular analyses in cell culture, we show that fgaB but not fgaA is induced in hypoxia, in a Sima-dependent manner, through a HIF-Responsive Element localized in the first intron of fgaA. The regulatory capacity of FgaB is stronger than that of FgaA, as complete reversion of fga loss-of-function phenotypes is observed upon transgenic expression of the former, and only partial rescue occurs after expression of the latter.
  
  
  CONCLUSIONS
  Diversity of PHD isoforms is a conserved feature in evolution. As in mammals, there are hypoxia-inducible and non-inducible Drosophila PHDs, and a fly isoform including a MYND domain co-exists with isoforms lacking this domain. Our results suggest that the isoform devoid of a MYND domain has stronger regulatory capacity than that including this domain.
authors.affiliation: Instituto Leloir, Buenos Aires, Argentina.
authors.forename: Julieta M
authors.initials: JM
authors.lastname: Acevedo
authors.forename: Lazaro
authors.initials: L
authors.lastname: Centanin
authors.forename: Andrés
authors.initials: A
authors.lastname: Dekanty
authors.forename: Pablo
authors.initials: P
authors.lastname: Wappner
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D056426:Genetic Loci / Q000235:genetics; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008018:Life Cycle Stages / Q000235:genetics; D010100:Oxygen / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; C100429:Sima protein, Drosophila; D011393:Procollagen-Proline Dioxygenase; D010100:Oxygen
references.citation: EMBO Rep. 2005 Nov;6(11):1070-5
references.pmid: 16179946
references.citation: J Biol Chem. 2009 Aug 21;284(34):23046-58
references.pmid: 19546213
references.citation: Proc Natl Acad Sci U S A. 1993 May 1;90(9):4304-8
references.pmid: 8387214
references.citation: Proc Natl Acad Sci U S A. 1995 Jun 6;92(12):5510-4
references.pmid: 7539918
references.citation: Blood. 2008 Mar 15;111(6):3229-35
references.pmid: 18056838
references.citation: Cell. 2001 Oct 5;107(1):1-3
references.pmid: 11595178
references.citation: Nat Rev Mol Cell Biol. 2004 May;5(5):343-54
references.pmid: 15122348
references.citation: Science. 2001 Apr 20;292(5516):464-8
references.pmid: 11292862
references.citation: Cell. 2001 Oct 5;107(1):43-54
references.pmid: 11595184
references.citation: Science. 2001 Nov 9;294(5545):1337-40
references.pmid: 11598268
references.citation: Mol Cell Biol. 2002 Oct;22(19):6842-53
references.pmid: 12215541
references.citation: Mol Cell Biol. 2007 May;27(10):3758-68
references.pmid: 17353276
references.citation: Science. 1999 Jul 23;285(5427):553-6
references.pmid: 10417378
references.citation: Cell Death Differ. 2008 Apr;15(4):635-41
references.pmid: 18259202
references.citation: J Biol Chem. 2002 Feb 15;277(7):4906-10
references.pmid: 11733528
references.citation: Dev Cell. 2008 Apr;14(4):547-58
references.pmid: 18410730
references.citation: J Biol Chem. 2005 Nov 11;280(45):38102-7
references.pmid: 16157596
references.citation: Dev Cell. 2004 Feb;6(2):241-51
references.pmid: 14960278
references.citation: Proc Natl Acad Sci U S A. 2005 May 24;102(21):7481-6
references.pmid: 15897452
references.citation: J Biol Chem. 2004 Sep 10;279(37):38458-65
references.pmid: 15247232
references.citation: EMBO J. 2003 Aug 15;22(16):4082-90
references.pmid: 12912907
references.citation: Genes Dev. 2003 Nov 1;17(21):2614-23
references.pmid: 14597660
references.citation: Biochem J. 2005 Aug 15;390(Pt 1):189-97
references.pmid: 15823097
references.citation: J Cell Sci. 2003 Apr 1;116(Pt 7):1319-26
references.pmid: 12615973
references.citation: J Cell Sci. 2005 Dec 1;118(Pt 23):5431-41
references.pmid: 16278294
references.citation: Nat Genet. 2008 Feb;40(2):170-80
references.pmid: 18176562
references.citation: Mol Pharmacol. 2005 Dec;68(6):1803-9
references.pmid: 16155211
references.citation: Science. 2001 Apr 20;292(5516):468-72
references.pmid: 11292861
references.citation: Proc Natl Acad Sci U S A. 1993 Mar 15;90(6):2423-7
references.pmid: 8460154
references.citation: EMBO J. 1998 Nov 16;17(22):6573-86
references.pmid: 9822602
references.citation: Sci STKE. 2005 Oct 18;2005(306):re12
references.pmid: 16234508