title: Rice serine/threonine kinase 1 is required for the stimulation of OsNug2 GTPase activity.
abstract: Several GTPases are required for ribosome biogenesis and assembly. We recently identified rice (Oryza sativa) nuclear/nucleolar GTPase 2 (OsNug2), a YlqF/YawG family GTPase, as having a role in pre-60S ribosomal subunit maturation. To investigate the potential factors involved in regulating OsNug2 function, yeast two-hybrid screens were performed using OsNug2 as bait. Rice serine/threonine kinase 1 (OsSTK1) was identified as a candidate interacting protein. OsSTK1 appeared to interact with OsNug2 both in vitro and in vivo. OsSTK1 was found to have no effect on the GTP-binding activity of OsNug2; however, the presence of recombinant OsSTK1 in OsNug2 assay reaction mixtures increased OsNug2 GTPase activity. A kinase assay showed that OsSTK1 had weak autophosphorylation activity and strongly phosphorylated serine 209 of OsNug2. Using yeast complementation testing, we identified a GAL::OsNug2(S209N) mutation-harboring yeast strain that exhibited a growth-defective phenotype on galactose medium at 39°C, which was divergent from that of a yeast strain harboring GAL::OsNug2. The intrinsic GTPase activity of OsNug2(S209N), which was found to be similar to that of OsNug2, was not fully enhanced upon weak binding of OsSTK1. Our findings indicate that OsSTK1 functions as a positive regulator of OsNug2 by enhancing OsNug2 GTPase activity. In addition, phosphorylation of OsNug2 serine 209 is essential for its complete function in biological functional pathway.
authors.affiliation: Department of Molecular Biotechnology, Dong-A University, Busan 604-714, South Korea. Electronic address: jbheo72@dau.ac.kr.
authors.forename: Jae Bok
authors.initials: JB
authors.lastname: Heo
authors.affiliation: Department of Molecular Biotechnology, Dong-A University, Busan 604-714, South Korea.
authors.forename: Yun Mi
authors.initials: YM
authors.lastname: Lee
authors.affiliation: Department of Molecular Biotechnology, Dong-A University, Busan 604-714, South Korea.
authors.forename: Hee Rang
authors.initials: HR
authors.lastname: Yun
authors.affiliation: Eco-friendliness Research Department, Gyeongsangnam-do Agricultural Research and Extension Services, Jinju 660-360, South Korea.
authors.forename: Chak Han
authors.initials: CH
authors.lastname: Im
authors.affiliation: Department of Biotechnology, Dong-A University, Busan 604-714, South Korea.
authors.forename: Yong-Suk
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Department of Molecular Biotechnology, Dong-A University, Busan 604-714, South Korea.
authors.forename: Young Byong
authors.initials: YB
authors.lastname: Yi
authors.affiliation: Department of Molecular Biology, Dankook University, Yongin 448-701, South Korea.
authors.forename: Chian
authors.initials: C
authors.lastname: Kwon
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, South Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Lim
authors.affiliation: Department of Biochemistry, Gyeongsang National University, Jinju 660-701, South Korea.
authors.forename: Jeong Dong
authors.initials: JD
authors.lastname: Bahk
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D009154:Mutation; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D017346:Protein Serine-Threonine Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins
keywords: GTP binding activity; GTPase activity; Kinase; OsNug2; OsSTK1