Reovirus protein lambda 3 is a poly(C)-dependent poly(G) polymerase

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Reovirus is a non-enveloped dsRNA virus with a segmented genome.
• Reovirus protein lambda 3 is a component of the viral core, implicated in RNA synthesis.
• Understanding the enzymatic activity and interactions of lambda 3 is crucial for deciphering viral replication.

Purpose of the Study:

• To isolate and characterize the enzymatic activity of reovirus protein lambda 3.
• To investigate the substrate specificity and cofactor preference of lambda 3.
• To examine the complex formation of lambda 3 with other reovirus proteins.

Main Methods:

• Recombinant vaccinia virus expression system was used to produce reovirus protein lambda 3.
• Enzymatic assays were performed using various RNA and synthetic polynucleotide templates.
• Co-immunoprecipitation assays were employed to study protein-protein interactions.

Main Results:

• Highly purified reovirus protein lambda 3 demonstrated transcriptase activity on poly(C) templates, producing poly(G).
• Lambda 3 showed a preference for Mn2+ over Mg2+ as a cofactor.
• Protein lambda 3 formed stable complexes with reovirus proteins lambda 1 and lambda 2, but these complexes lacked RNA transcriptase activity.

Conclusions:

• Reovirus protein lambda 3 possesses a specific RNA-dependent RNA polymerase activity, synthesizing poly(G) from poly(C).
• Lambda 3's interaction with lambda 1 and lambda 2 is essential for forming functional viral transcription complexes.
• Despite forming complexes, lambda 3 alone or in these complexes does not transcribe double-stranded or single-stranded reovirus RNA.