title: Kinetics of dephosphorylation of eIF-2(alpha P) and reutilization of mRNA.
abstract: Phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2) causes mRNA to accumulate in 48 S complexes containing Met-tRNAf and eIF-2(alpha P). When the eIF-2 alpha kinase is inhibited by 2-aminopurine, the mRNA is slowly transferred from 48 to 80 S initiation complexes after an initial lag. The cause of this lag was examined by investigating whether mRNA and Met-tRNAf dissociated from 48 S complexes before binding to 80 S. Both compounds were quantitatively transferred from 48 to 80 S complexes after addition of 2-aminopurine and the eIF-2(alpha P) bound to 48 S complexes was dephosphorylated after an initial lag more slowly than unbound eIF-2(alpha P), which was rapidly dephosphorylated. the eIF-2(alpha P) in isolated 48 S complexes was slowly dephosphorylated by partially purified lysate phosphatases, whereas free eIF-2(alpha P) was readily dephosphorylated. These results indicated that 48 S complexes could directly join to a 60 S ribosomal subunit after eIF-2(alpha P) dephosphorylation. The lag and slow kinetics of dephosphorylation of eIF-2(alpha P) bound to 48 S complexes accounted for the slow transfer of mRNA from 48 to 80 S complexes. Moreover, the mRNA bound to 48 S complexes was more susceptible to cleavage by an endonuclease than mRNA in polyribosomes, as shown by activating the (2'-5')oligo(A)-dependent endonuclease. This finding is discussed in view of the possible role of eIF-2 alpha kinase and endonuclease in the inhibition of viral mRNA translation in interferon-treated cells.
authors.forename: A
authors.initials: A
authors.lastname: De Benedetti
authors.forename: C
authors.initials: C
authors.lastname: Baglioni
mesh_terms: D004722:Endoribonucleases / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012358:RNA, Transfer, Met; D012367:RNA, Viral / Q000378:metabolism; D014721:Vesicular stomatitis Indiana virus / Q000235:genetics
chemical_list: D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011506:Proteins; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; D012367:RNA, Viral; C024988:tRNA, formylmethionine-; C033547:2'-5'-oligo(A)-dependent endonuclease; D004722:Endoribonucleases