ABSTRACT
Translation initiation on EMCV RNA occurs via binding of ribosomes to an internal sequence within the 5' noncoding region. To investigate the organization of the internal ribosome entry site (IRES) we have determined the translational efficiencies of a series of deletion mutants within the 5' noncoding region of EMCV RNA. Three functional regions have been distinguished: a sequence between nts 315-484 and the upper parts of the double-helical structural domains III (nts 488-647) and IV (nts 701-763). The first one greatly enhances translation, but is not absolutely necessary for internal initiation. The other two regions are indispensable to this process. A sequence within domain IV determines inhibition of in vitro translation of mRNAs with 5'-terminal dependent initiation. It is proposed to interact with a translational factor(s) common to the internal and 5'-terminal dependent initiation.
Subject(s)
Encephalomyocarditis virus/genetics , Protein Biosynthesis , RNA, Messenger/genetics , RNA, Viral/genetics , Ribosomes/metabolism , Binding Sites , Binding, Competitive , Cloning, Molecular , DNA Mutational Analysis , Hydrogen Bonding , Molecular Structure , RNA, Messenger/ultrastructure , RNA, Viral/ultrastructure , Regulatory Sequences, Nucleic Acid , Restriction MappingSubject(s)
Carcinoma, Krebs 2/metabolism , Encephalomyocarditis virus , RNA, Transfer, Amino Acyl/metabolism , Animals , Cell Line , Eukaryotic Initiation Factor-2 , Guanosine Triphosphate/metabolism , Magnesium/pharmacology , Mice , Peptide Initiation Factors/metabolism , Proteins/metabolism , Ribosomes/metabolismSubject(s)
Carcinoma, Hepatocellular/metabolism , Liver Neoplasms/metabolism , Liver/metabolism , Neoplasm Proteins/biosynthesis , Nitrosourea Compounds/pharmacology , Protein Biosynthesis , Animals , Carbon Radioisotopes , Cell-Free System , In Vitro Techniques , Kinetics , Male , Mice , Mice, Inbred C3H , Mitochondria, Liver/metabolism , Neoplasms, Experimental/metabolism , Ribosomes/metabolism , Time FactorsABSTRACT
The relative efficiency of translation of host cell mRNA and encephalomyocarditis (emc) virus RNA has been investigated in cell-free preparations from uninfected and EMC virus-infected Drebs-II cells. The ability of cell-free extracts from infected cells to translate exogenously-added EMC virus RNA and total Krebs-II cell mRNA was markedly diminished, but no evidence for the selective inhibition of translation of host cell mRNA in these systems was obtained.
