Early effects of dimethylnitrosamine on the initiation of protein synthesis in mouse liver.
1. Dimethylnitrosamine (37.5 mg/kg body wt.) was administered to mice by a single intraperitoneal injection, and the early effects on protein synthesis and related functions were studied in a liver S-30 system. 2. The incorporation of [14C]leucine into protein decreased rapidly after dimethylnitrosamine administration. The effect was associated with a decreased ability of the system to utilize methionyl-tRNAfMet and formyl-methionyl-tRNAfMet for 80 S ribosomal initiation-complex formation (primary initiation), and a loss of poly(A)-containing RNA from the postmicrosomal fraction. All the three effects developed simultaneously, and were clearly demonstrable within 15 min. 3. Initiation-complex formation in the polyribosomal fraction (re-initiation) was decreased to the same extent as the primary initiation, indicating that the initiation defect was not a result of the decrease in free mRNA. 4. The inhibition of initiation was only manifest at the joining of the 40 S pre-initiation complex to 60 S ribosomal subunits. It was not a result of methionyl-tRNAfMet deacylation. The functions between the formation of the methionyl-tRNAfMet-containing 80 S ribosomal complex and the first translocation on the ribosome were not involved, since the incorporation of formylmethionine into N-terminal polypeptides decreased to the same extent as the 80 S initiation-complex formation. 5. Inhibitors of protein synthesis (cycloheximide and pactamycin) decreased poly(A)-containing RNA in the postmicrosomal fraction in a similar way to dimethylnitrosamine.
D000818:Animals; D004128:Dimethylnitrosamine / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D010452:Peptide Biosynthesis; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D011061:Poly A / Q000032:analysis; D014176:Protein Biosynthesis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors
D012346:RNA, Transfer, Amino Acyl; C026464:tRNA(m)(Met), methionine-; D011061:Poly A; D004128:Dimethylnitrosamine