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Internal ribosome entry site within hepatitis C virus RNA
K Tsukiyama-Kohara1, N Iizuka, M Kohara
1Department of Microbiology, Tokyo Metropolitan Institute of Medical Science, Japan.
Journal of Virology
|March 1, 1992
Summary
Hepatitis C virus (HCV) RNA translation initiates internally, not at the 5' cap. This internal ribosome entry site (IRES) is located between nucleotides 101-332, crucial for efficient protein synthesis.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Hepatitis C virus (HCV) is a major cause of chronic liver disease.
- Understanding viral RNA translation is key to developing antiviral therapies.
Purpose of the Study:
- To investigate the mechanism of translation initiation on HCV RNA.
- To identify the specific region responsible for internal ribosome entry.
Main Methods:
- In vitro transcription of HCV RNA using phage T7 RNA polymerase.
- Cell-free protein synthesis assays with HeLa S3 and rabbit reticulocyte lysates.
- Analysis of translation products using anti-gp35 antibodies.
- Construction and testing of artificial mono- and dicistronic mRNAs.
Main Results:
- HCV RNA translation initiates at the fourth AUG (position 333), independent of the 5' cap in some systems.
- A capped methylated RNA showed higher activity than unmethylated RNA when upstream sequences were absent.
- Evidence strongly suggests the presence of an internal ribosome entry site (IRES) on HCV RNA.
- The IRES activity was mapped to the 5' untranslated region between nucleotides 101 and 332.
- Group II HCV RNA demonstrated a more efficient IRES than Group I.
Conclusions:
- HCV RNA utilizes an internal ribosome entry site (IRES) for translation initiation.
- The 5' untranslated region, specifically nucleotides 101-332, contains the functional IRES.
- This IRES mechanism is critical for efficient HCV protein synthesis and viral replication.