title: Oxygen-regulated degradation of fission yeast SREBP by Ofd1, a prolyl hydroxylase family member.
abstract: Sre1, the fission yeast sterol regulatory element binding protein, is an endoplasmic reticulum membrane-bound transcription factor that responds to changes in oxygen-dependent sterol synthesis as an indirect measure of oxygen availability. Under low oxygen, Sre1 is proteolytically cleaved and the released N-terminal transcription factor (Sre1N) activates gene expression essential for hypoxic growth. Here, we describe an oxygen-dependent mechanism for regulation of Sre1 that is independent of sterol-regulated proteolysis. Using yeast expressing only Sre1N, we show that Sre1N turnover is regulated by oxygen. Ofd1, an uncharacterized prolyl 4-hydroxylase-like 2-oxoglutarate-Fe(II) dioxygenase, accelerates Sre1N degradation in the presence of oxygen. However, unlike the prolyl 4-hydroxylases that regulate mammalian hypoxia-inducible factor, Ofd1 uses multiple domains to regulate Sre1N degradation by oxygen; the Ofd1 N-terminal dioxygenase domain is required for oxygen sensing and the Ofd1 C-terminal domain accelerates Sre1N degradation. Our data support a model whereby the Ofd1 N-terminal dioxygenase domain is an oxygen sensor that regulates the activity of the C-terminal degradation domain.
authors.affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Bridget T
authors.initials: BT
authors.lastname: Hughes
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Espenshade
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D006801:Humans; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D051779:Sterol Regulatory Element Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029702:Schizosaccharomyces pombe Proteins; C500467:Sre1 protein, S pombe; D051779:Sterol Regulatory Element Binding Proteins; D011393:Procollagen-Proline Dioxygenase; D046988:Proteasome Endopeptidase Complex; D010100:Oxygen