Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The adenovirus tripartite leader (TPT) 5' untranslated region (5'UTR) allows translation in poliovirus-infected cells, in which the p220 subunit of eukaryotic initiation factor 4F is degraded. This p220-independent translation was investigated by measuring in vitro translation in a reticulocyte lysate of a reporter gene, chloramphenicol acetyltransferase, coupled to the TPT 5'UTR. The p220 subunit was degraded by translation of a foot-and-mouth-disease L-protease construct. Surprisingly, the TPT 5'UTR was dependent on intact p220, as are other naturally capped mRNA species. Translation of encephalomyocarditis virus RNA was p220 independent, as expected from its ability to support internal, cap-independent initiation. In vitro protein-synthesis experiments with purified initiation factors confirmed the dependence of TPT mRNA translation on eukaryotic initiation factor 4F. The relationship between adenovirus TPT-5'UTR-directed translation and poliovirus-induced host cell shut-off is discussed.
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PMID:Dependence of the adenovirus tripartite leader on the p220 subunit of eukaryotic initiation factor 4F during in vitro translation. Effect of p220 cleavage by foot-and-mouth-disease-virus L-protease on in vitro translation. 132 14

To characterize in vivo the translational control elements present in the 5' nontranslated region (5'NTR) of hepatitis A virus (HAV) RNA, we created an HAV-permissive monkey kidney cell line (BT7-H) that stably expresses T7 RNA polymerase and carries out cytoplasmic transcription of uncapped RNA from transfected DNA containing the T7 promoter. The presence of an internal ribosomal entry site (IRES) within the 5'NTR of HAV was confirmed by using BT7-H cells transcribing bicistronic RNAs in which the 5'NTR was placed within the intercistronic space, controlling translation of a downstream reporter protein (bacterial chloramphenicol acetyltransferase). However, translation directed by the 5'NTR in these bicistronic transcripts and in monocistronic T7 transcripts in which the HAV 5'NTR was placed upstream of the chloramphenicol acetyltransferase coding sequence was very inefficient compared with the translation of monocistronic transcripts containing either the IRES of encephalomyocarditis (EMC) virus or a short nonpicornavirus 5' nontranslated leader sequence. A large deletion within the HAV IRES (delta 355-532) eliminated IRES activity in bicistronic transcripts. In contrast, larger deletions within the IRES in monocistronic transcripts (delta 1-354, delta 1-532, delta 1-633, and delta 158-633) resulted in 4- to 14-fold increases in translation. In the latter case, this was most probably due to a shift from IRES-directed translation to translation initiation by 5'-end-dependent scanning. Translation of RNAs containing either the EMC virus IRES or the nonpicornavirus leader was significantly enhanced by cotransfection of the reporter constructs with pEP2A, which directs transcription of RNA containing the EMC virus IRES fused to the poliovirus 2Apro coding region. This 2Apro enhancement of cap-independent translation suggests a greater availability of limiting cellular translation factors following 2Apro-mediated cleavage of the p220 subunit of the eukaryotic initiation factor eIF-4F and subsequent shutdown of 5' cap-dependent translation. In contrast, pEP2A cotransfection resulted in severe inhibition of translation directed by the HAV IRES in either monocistronic or bicistronic transcripts. This inhibition was due to competition from the EMC virus IRES present in pEP-2A transcripts, as well as the expression of proteolytically active 2Apro. 2Apro-mediated suppression of HAV translation was not seen with transcripts containing large deletions in the HAV IRES (delta 158-633, delta 1-532, or delta 1-633). These data suggest that the HAV IRES may have a unique requirement for intact p220 or that it may be dependent on active expression of another cellular translation factor which is normally present in severely limiting quantities.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Low efficiency of the 5' nontranslated region of hepatitis A virus RNA in directing cap-independent translation in permissive monkey kidney cells. 803 22