title: HIF-1alpha and -2alpha genes in a hypoxia-sensitive teleost species Megalobrama amblycephala: cDNA cloning, expression and different responses to hypoxia.
abstract: Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor (HIF) alpha subunits, i.e. HIF-1alpha, -2alpha and -3alpha. In fish, the molecular constructions, expression characteristics and hypoxic regulation of HIF-alpha subunits are still not well known. In this study, we identified the HIF-1alpha and HIF-2alpha full-length cDNAs in a hypoxia-sensitive fish species Wuchang bream, Megalobrama amblycephala. The whole length of HIF-1alpha cDNA was 3,815bp, consisting of an open reading frame (ORF) encoding 774 amino acid (aa) residues. The HIF-2alpha cDNA totaled 3,121-bp including an 835-aa ORF. The Wuchang bream HIF-1alpha and HIF-2alpha subunits were structurally similar in the DNA-binding and dimerization domains, but differed in the transactivation domain. In adult fish, both HIF-1alpha and HIF-2alpha mRNAs were detected in different tissues under normoxic conditions. HIF-1alpha mRNA was highly expressed in the liver, gill and testis, whereas HIF-2alpha mRNA was abundantly expressed in most of the Wuchang bream tissues. Both HIF-1alpha and HIF-2alpha mRNAs were detected in all stages of embryogenesis and expressed in a ubiquitous pattern. In contrast to HIF-1alpha, the mRNA levels of HIF-2alpha fluctuated in different stages, with higher expression in the zygote, 8-, 28-, 48- and 52-hr post fertilization (hpf) embryos. During hypoxic treatment, the mRNA levels of HIF-2alpha were significantly (p<0.01) up-regulated to 910% in the liver and 320% in the kidney, whereas no significant changes of HIF-1alpha mRNA were observed in the corresponding tissues. These results suggest that the Wuchang bream HIF-1alpha and -2alpha would be involved in different physiological functions under normoxia and hypoxia situations.
authors.affiliation: Key Laboratory of Aquatic Genetic Resources, Shanghai Ocean University, Huchenghuan Road 999, Shanghai 201306, China.
authors.forename: Rui-Jie
authors.initials: RJ
authors.lastname: Shen
authors.forename: Xia-Yun
authors.initials: XY
authors.lastname: Jiang
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Pu
authors.forename: Shu-Ming
authors.initials: SM
authors.lastname: Zou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia; D003001:Cloning, Molecular; D003530:Cyprinidae / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D016415:Sequence Alignment; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018076:DNA, Complementary; D029941:Fish Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D000099162:Endothelial PAS Domain-Containing Protein 1