Ribosome binding to reovirus mRNA in protein synthesis requires 5' terminal 7-methylguanosine.

摘要: Abstract Purified reovirus synthesizes in vitro a mixture of mRNA molecules that contain 5′ terminal structures the type ppG…, GpppG…, and m 7 GpppG , relative amount each depending upon presence S-adenosylmethionine (SAM) or S-adenosylhomocysteine (SAH) transcription incubation mixture. Reovirus mRNAs containing termini ppG… GpppG… can be specifically modified by wheat germ extracts SAM to yield structure (Muthukrishnan et al., 1975). The methylase activity is ribosome-independent recovered almost entirely high speed supernatant fraction extracts. Its inhibited aurintricarboxylic acid. Ribosome binding experiments with extract indicate only those G are capable participating initiation protein synthesis subsequent polysome formation. unmethylated do not form complex 40S ribosomal subunits. Discrimination between methylated mRNA, active synthesis, apparently occurs at before formation 40S-mRNA complexes. T1 pancreatic RNAase digestion bound 80S ribosomes yields fragments apparent chain lengths about 32 36 nucleotides, respectively. A portion RNAase-resistant rebinds nuclease-resistant complex. In contrast, shorter oligonucleotide pCpUp(Np) 3 Gp derived purified does bind ribosomes. results suggest may function as primary recognition signal for ribosome very close some species mRNAs.