Coding from a distance: dissection of the mRNA determinants required for the incorporation of selenocysteine into protein.
Incorporation of selenocysteine into proteins is directed by specifically 'programmed' UGA codons. The determinants for recognition of the selenocysteine codon have been investigated by analysing the effect of mutations in fdhF, the gene for formate dehydrogenase H of Escherichia coli, on selenocysteine incorporation. It was found that selenocysteine was also encoded when the UGA codon was replaced by UAA and UAG, provided a proper codon-anticodon interaction was possible with tRNA(Sec). This indicates that none of the three termination codons can function as efficient translational stop signals in that particular mRNA position. The discrimination of the selenocysteine 'sense' codon from a regular stop codon has previously been shown to be dependent on an RNA secondary structure immediately 3' of the UGA codon in the fdhF mRNA. It is demonstrated here that the correct folding of this structure as well as the existence of primary sequence elements located within the loop portion at an appropriate distance to the UGA codon are absolutely required. A recognition sequence can be defined which mediates specific translation of a particular codon inside an mRNA with selenocysteine and a model is proposed in which translation factor SELB interacts with this recognition sequence, thus forming a quaternary complex at the mRNA together with GTP and selenocysteyl-tRNA(Sec).
Heider
J
J
Lehrstuhl für Mikrobiologie, Universität München, FRG.
Baron
C
C
Böck
A
A
D000926:Anticodon / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D005560:Formate Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D006864:Hydrogenase / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015183:Restriction Mapping; D017279:Selenocysteine / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D000926:Anticodon; D003062:Codon; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D017279:Selenocysteine; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase; D001616:beta-Galactosidase