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Secondary structure and mutational analysis of the Mason-Pfizer monkey virus RNA constitutive transport element
1Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, University of Virginia, Charlottesville 22908, USA.
Abstract:
The Mason-Pfizer monkey virus (MPMV) genome contains a cis-acting element that serves to facilitate nucleocytoplasmic export of intron-containing RNA. This element, known as the constitutive transport element (CTE), has been mapped to a 154-nt region close to the 3' end of the MPMV genome. The CTE contains a degenerate direct repeat of approximately 70 nt. We have probed the secondary structure of the CTE using double-strand- and single-strand-specific ribonucleases and chemical modification agents. A mutational analysis was also performed to confirm critical features of the CTE structure, as well as to identify regions that contain sequence-specific information required for function. Our results indicate that the CTE forms a long stem structure that contains a 9-nt terminal hairpin loop as well as two identical 16-nt inner loops. The inner loop sequences are rotated 180 degrees relative to each other within the structure. The mutational analysis shows that primary sequences in the loop regions are important for function, suggesting that they may contain binding sites for cellular proteins involved in RNA export. Interestingly, sequences with significant homology to the inner loop regions are found in the genomes of spumaviruses and mouse intracisternal A particles.
Insights
The Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE) facilitates RNA export. Structural analysis reveals a stem-loop formation crucial for cellular protein binding and function.
Area of Science:
- Molecular Biology
- Virology
- RNA Biology
Background:
- The Mason-Pfizer monkey virus (MPMV) genome possesses a cis-acting element facilitating RNA export.
- This element, the constitutive transport element (CTE), is located near the 3' end of the viral genome.
Purpose of the Study:
- To elucidate the secondary structure of the MPMV CTE.
- To identify sequence-specific regions critical for CTE function in RNA export.
Main Methods:
- Probing RNA secondary structure using ribonucleases and chemical modification agents.
- Performing mutational analysis to assess the functional importance of CTE regions.
Main Results:
- The CTE forms a stem structure with a terminal hairpin loop and two identical inner loops.
- Mutational analysis confirmed the importance of primary sequences within the loop regions for CTE function.
- Homologous sequences to CTE inner loops were identified in spumaviruses and mouse intracisternal A particles.
Conclusions:
- The CTE's secondary structure, particularly its loops, is essential for its role in nucleocytoplasmic RNA export.
- The loop regions likely serve as binding sites for cellular proteins mediating RNA export.
- Structural similarities suggest a conserved mechanism for RNA export elements across different viruses and genetic elements.