Supramolecular complexes mediate selenocysteine incorporation in vivo.
Selenocysteine incorporation in eukaryotes occurs cotranslationally at UGA codons via the interactions of RNA-protein complexes, one comprised of selenocysteyl (Sec)-tRNA([Ser]Sec) and its specific elongation factor, EFsec, and another consisting of the SECIS element and SECIS binding protein, SBP2. Other factors implicated in this pathway include two selenophosphate synthetases, SPS1 and SPS2, ribosomal protein L30, and two factors identified as binding tRNA([Ser]Sec), termed soluble liver antigen/liver protein (SLA/LP) and SECp43. We report that SLA/LP and SPS1 interact in vitro and in vivo and that SECp43 cotransfection increases this interaction and redistributes all three proteins to a predominantly nuclear localization. We further show that SECp43 interacts with the selenocysteyl-tRNA([Ser]Sec)-EFsec complex in vitro, and SECp43 coexpression promotes interaction between EFsec and SBP2 in vivo. Additionally, SECp43 increases selenocysteine incorporation and selenoprotein mRNA levels, the latter presumably due to circumvention of nonsense-mediated decay. Thus, SECp43 emerges as a key player in orchestrating the interactions and localization of the other factors involved in selenoprotein biosynthesis. Finally, our studies delineating the multiple, coordinated protein-nucleic acid interactions between SECp43 and the previously described selenoprotein cotranslational factors resulted in a model of selenocysteine biosynthesis and incorporation dependent upon both cytoplasmic and nuclear supramolecular complexes.
Small-Howard
Andrea
A
Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
Morozova
Nadya
N
Stoytcheva
Zoia
Z
Forry
Erin P
EP
Mansell
John B
JB
Harney
John W
JW
Carlson
Bradley A
BA
Xu
Xue-Ming
XM
Hatfield
Dolph L
DL
Berry
Marla J
MJ
D001324:Autoantigens / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D018388:Codon, Terminator; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D046912:Multiprotein Complexes / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012362:RNA, Transfer, Ser / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017279:Selenocysteine / Q000378:metabolism*; D051140:Selenoproteins / Q000096:biosynthesis / Q000378:metabolism
D001324:Autoantigens; D018388:Codon, Terminator; C509159:EFsec protein, mouse; D046912:Multiprotein Complexes; D010445:Peptide Elongation Factors; D012333:RNA, Messenger; D012362:RNA, Transfer, Ser; D016601:RNA-Binding Proteins; C121530:SECISBP2 protein, human; D051140:Selenoproteins; C402594:Trnau1ap protein, rat; C046431:liver antigen LA-1; D017279:Selenocysteine; D010770:Phosphotransferases; C062762:selenophosphate synthetase