Poliovirus replicase stimulation by terminal uridylyl transferase

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Poliovirus replication requires viral polymerase, sense RNA, and a host factor for minus-strand synthesis.
• Previous studies identified essential components for in vitro poliovirus replication.

Purpose of the Study:

• To identify alternative factors that can substitute for the host factor in poliovirus replicase reactions.
• To investigate the enzymatic activities present in the substitute fraction and their roles in replication.

Main Methods:

• Utilized an in vitro poliovirus replication system.
• Employed partially purified eukaryotic initiation factor-2 (eIF-2) fraction from rabbit reticulocytes.
• Assayed for terminal uridylyl transferase activity and its dependence on primer type and reaction components.

Main Results:

• A partially purified eIF-2 fraction from rabbit reticulocytes effectively replaced the HeLa host factor in the poliovirus replicase reaction.
• This fraction contained terminal uridylyl transferase activity, which adds UMP moieties to RNA primers.
• Terminal uridylyl transferase activity demonstrated primer-dependent polymerization and required UTP, Mg2+, a sulfhydryl reagent, and an RNA primer.

Conclusions:

• Terminal uridylyl transferase activity, found in the eIF-2 fraction, shows preliminary evidence of host factor-like activity in poliovirus replication.
• A model is proposed where terminal uridylyl transferase participates in the initiation of minus-strand synthesis by poliovirus replicase.