title: Selenophosphate synthetase 2 is essential for selenoprotein biosynthesis.
abstract: Selenophosphate synthetase (SelD) generates the selenium donor for selenocysteine biosynthesis in eubacteria. One homologue of SelD in eukaryotes is SPS1 (selenophosphate synthetase 1) and a second one, SPS2, was identified as a selenoprotein in mammals. Earlier in vitro studies showed SPS2, but not SPS1, synthesized selenophosphate from selenide, whereas SPS1 may utilize a different substrate. The roles of these enzymes in selenoprotein synthesis in vivo remain unknown. To address their function in vivo, we knocked down SPS2 in NIH3T3 cells using small interfering RNA and found that selenoprotein biosynthesis was severely impaired, whereas knockdown of SPS1 had no effect. Transfection of SPS2 into SPS2 knockdown cells restored selenoprotein biosynthesis, but SPS1 did not, indicating that SPS1 cannot complement SPS2 function. These in vivo studies indicate that SPS2 is essential for generating the selenium donor for selenocysteine biosynthesis in mammals, whereas SPS1 probably has a more specialized, non-essential role in selenoprotein metabolism.
authors.affiliation: Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Xue-Ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Carlson
authors.forename: Robert
authors.initials: R
authors.lastname: Irons
authors.forename: Heiko
authors.initials: H
authors.lastname: Mix
authors.forename: Nianxin
authors.initials: N
authors.lastname: Zhong
authors.forename: Vadim N
authors.initials: VN
authors.lastname: Gladyshev
authors.forename: Dolph L
authors.initials: DL
authors.lastname: Hatfield
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015152:Blotting, Northern; D003001:Cloning, Molecular; D051379:Mice; D018345:Mice, Knockout; D010770:Phosphotransferases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D034741:RNA, Small Interfering; D011994:Recombinant Proteins / Q000378:metabolism; D051140:Selenoproteins / Q000096:biosynthesis*
chemical_list: D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D051140:Selenoproteins; D012313:RNA; D010770:Phosphotransferases; C499551:Sephs2 protein, mouse; C062762:selenophosphate synthetase