Binding of mammalian ribosomes to MS2 phage RNA reveals an overlapping gene encoding a lysis function

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Bacteriophage MS2 RNA contains overlapping genes, with a lysis gene downstream of the coat protein gene.
• Mammalian ribosomes can initiate translation at an AUG codon within the coat protein gene, producing a lysis polypeptide.
• The op3 mutation in phage f2 affects lysis and replicase production.

Purpose of the Study:

• To characterize the overlapping lysis gene in bacteriophage MS2.
• To investigate the role of the op3 mutation in phage gene expression and function.
• To compare ribosome binding and translation initiation between prokaryotic and eukaryotic systems.

Main Methods:

• RNA-directed protein synthesis using mammalian and E. coli cell-free systems.
• Partial amino acid sequence analysis of synthesized polypeptides.
• Genetic analysis of the op3 mutation in phage f2.

Main Results:

• Mammalian ribosomes efficiently translate a 75-amino acid lysis polypeptide from bacteriophage MS2 RNA.
• The op3 mutation is a C-to-U transition in the synthetase cistron, affecting lysis and replicase production.
• E. coli cell-free systems produce very small amounts of the lysis polypeptide compared to mammalian systems.

Conclusions:

• The overlapping lysis gene is efficiently translated by mammalian ribosomes.
• The op3 mutation disrupts the lysis initiator region, impacting both lysis and replicase synthesis.
• Differences in ribosome recognition of the lysis initiator region exist between E. coli and mammalian systems.