Transcript leader regions of two Saccharomyces cerevisiae mRNAs contain internal ribosome entry sites that function in living cells

摘要: Abstract In higher eukaryotes, translation of some mRNAs occurs by internal initiation. It is not known, however, whether this mechanism used to initiate the any yeast mRNAs. In report, we identify naturally occurring nucleotide sequences that function as ribosome entry sites (IRESes) within 5′ leader Saccharomyces cerevisiae YAP1 and p150 When tested in untranslated regions monocistronic reporter genes, both enhanced efficiency vegetatively growing cells. Moreover, when intercistronic region dicistronic mRNAs, were shown contain IRESes functioned living The activity was much greater than leader. second cistron expressed control constructs lacked these or contained sequence CLN3 mRNA region. Further analyses IRES revealed it several nonoverlapping segments able independently mediate These results suggested a modular composition for resembled cellular eukaryotes. Both leaders complementary matches 18S rRNA. findings are discussed terms our understanding initiation