Vaccinia virus encodes a polypeptide with DNA ligase activity

Area of Science:

• Molecular Biology
• Virology
• Enzymology

Background:

• Vaccinia virus, a large DNA virus, possesses genes with unknown functions.
• DNA ligases are essential enzymes involved in DNA replication, repair, and recombination.
• The vaccinia virus SalF 15R gene was hypothesized to encode a DNA ligase.

Purpose of the Study:

• To investigate the function of the vaccinia virus SalF 15R gene.
• To identify and characterize a potential DNA ligase encoded by vaccinia virus.

Main Methods:

• Radio-labeling assays using alpha-(32P)ATP to detect DNA ligase activity.
• Enzyme assays to measure DNA ligase activity in infected cell extracts.
• Immunoprecipitation using antiserum against the SalF 15R protein.

Main Results:

• A novel 61 kD radio-labeled polypeptide was detected in vaccinia virus-infected cells incubated with alpha-(32P)ATP.
• This polypeptide formed a covalent adduct with AMP, characteristic of DNA ligases.
• Enzyme activity assays revealed increased DNA ligase activity post-infection.
• Antiserum against SalF 15R immunoprecipitated the 61 kD polypeptide and the DNA ligase-AMP adduct.

Conclusions:

• The vaccinia virus gene SalF 15R encodes a functional DNA ligase.
• This viral DNA ligase is present throughout infection and its activity increases during the infection process.
• The identified DNA ligase is likely involved in viral DNA replication or other essential viral processes.