Related Experiment Video
Updated: Aug 17, 2026
Using Reverse Genetics to Manipulate the NSs Gene of the Rift Valley Fever Virus MP-12 Strain to Improve Vaccine Safety and Efficacy
Published on: November 1, 2011
Alternative translation initiation site in the DA strain of Theiler's murine encephalomyelitis virus
Abstract:
Polyprotein processing studies of Theiler's murine encephalomyelitis virus (TMEV), a group of mouse picornaviruses, demonstrated synthesis of a protein we have called l during in vitro translations from the RNA of DA, a demyelinating strain of TMEV, but not GDVII, an acute neurovirulent strain. We have proposed that l is synthesized from an alternative initiation site in the DA leader (L) coding area out of phase with the polyprotein reading frame (R. P. Roos, W.-P. Kong, B. L. Semler, J. Virol. 63:5344-5353, 1989). We now provide support for this proposal from experiments involving in vitro translation of three separate mutations of an infectious DA cDNA clone: DA"l"-1, which contains a base mismatch at the putative initiation codon of l, DAL-1, which contains a base mismatch at the presumed authentic initiation site of L at the beginning of the polyprotein; and DAL:NheI, which contains nucleotides coding for a four-amino-acid insertion in the L coding area with a termination codon in the l reading frame. Our results demonstrate that the DA strain uses an alternative initiation site and reading frame to in vitro synthesize l. l may have a role in the biological activity of the virus.
Insights
Theiler's murine encephalomyelitis virus (TMEV) DA strain synthesizes a unique protein (l) via an alternative initiation site and reading frame. This finding provides insight into TMEV genetic mechanisms and potential biological roles.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Theiler's murine encephalomyelitis virus (TMEV) is a group of mouse picornaviruses.
- Different strains, like DA (demyelinating) and GDVII (neurovirulent), exhibit distinct biological activities.
- Previous studies suggested alternative protein synthesis in the DA strain.
Purpose of the Study:
- To investigate the synthesis of a protein designated 'l' in TMEV.
- To determine if 'l' is produced from an alternative initiation site and reading frame in the DA strain.
- To provide experimental support for the proposed alternative translation mechanism.
Main Methods:
- In vitro translation assays using RNA from TMEV strains.
- Site-directed mutagenesis of an infectious DA cDNA clone.
- Analysis of three specific mutations: DA"l"-1, DAL-1, and DAL:NheI.
- Examination of protein synthesis patterns based on genetic modifications.
Main Results:
- The DA strain of TMEV synthesized protein 'l' during in vitro translation.
- Mutational analysis confirmed the use of an alternative initiation site and reading frame for 'l' synthesis.
- The GDVII strain did not produce protein 'l' under similar conditions.
Conclusions:
- The DA strain of TMEV utilizes an alternative initiation site and reading frame to synthesize protein 'l'.
- Protein 'l' may play a role in the biological activity of TMEV.
- This study elucidates a novel aspect of TMEV gene expression.
Related Concept Videos
02:33Initiation of Translation
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
02:28Leaky Scanning