Endodeoxyribonuclease activity associated with Rauscher murine leukemia virus

Area of Science:

• Virology
• Molecular Biology
• Enzymology

Background:

• Rauscher murine leukemia virus (RMLV) is a retrovirus known to possess various enzymatic activities essential for its replication cycle.
• The specific endonuclease responsible for DNA processing within RMLV has not been definitively identified.

Purpose of the Study:

• To identify and characterize the endonuclease activity present in purified Rauscher murine leukemia virus preparations.
• To determine the molecular origin and properties of the RMLV-coded endonuclease.

Main Methods:

• Virus disruption using nonionic detergents to release intracellular enzymes.
• Enzyme partial purification via ion-exchange chromatography (DEAE- and carboxymethyl-Sepharose) and polyacrylamide gel electrophoresis.
• Peptide mapping to compare protein fragments and determine precursor relationships.

Main Results:

• An endodeoxyribonuclease activity was detected and partially purified from RMLV.
• The purified enzyme preparation was free of detectable reverse transcriptase activity.
• A 40,000 Mr polypeptide (p40) was identified as the likely endonuclease component.
• Peptide mapping revealed that p40 shares tryptic peptides with RMLV gag-pol precursors (Pr200gag-pol and Pr135pol).
• p40 exhibits similarities in size and precursor origin to the avian retrovirus endonuclease (p32).

Conclusions:

• The identified endodeoxyribonuclease, p40, is proposed to be the Rauscher murine leukemia virus-coded endonuclease.
• p40 plays a role in viral DNA processing, analogous to avian retrovirus endonucleases.
• Further characterization of p40 will elucidate its precise function in the RMLV replication cycle.