Horizontal acquisition of a DNA ligase improves DNA damage tolerance in eukaryotes

Area of Science:

• Molecular Biology
• Genetics
• Evolutionary Biology

Background:

• Bdelloid rotifers exhibit remarkable resistance to genotoxic stresses.
• Understanding the molecular mechanisms behind this extreme tolerance is crucial.

Purpose of the Study:

• To investigate the molecular basis of extreme radiation tolerance in the bdelloid rotifer Adineta vaga.
• To identify novel DNA repair mechanisms contributing to stress resistance.

Main Methods:

• Proteomic analysis of Adineta vaga exposed to ionizing radiation.
• Phylogenetic analysis to determine the origin of identified DNA ligases.
• Functional assays including heterologous expression in human cell lines.

Main Results:

• A specific DNA ligase (DNA ligase E), distinct from typical eukaryotic repair enzymes, was found to be over-represented after radiation exposure.
• Phylogenetic analysis indicated horizontal gene transfer of this enzyme from prokaryotes to bdelloid rotifers.
• The fungus Mortierella verticillata also showed increased radiation tolerance and DNA ligase E over-expression following X-ray exposure.
• Adineta vaga ligase E demonstrated significant DNA break ligation activity, crucial for DNA repair pathways.
• Heterologous expression of Adineta vaga ligase E in human cells enhanced their radio-tolerance.

Conclusions:

• Horizontal gene transfer can provide eukaryotes with adaptive advantages, such as extreme stress tolerance.
• DNA ligase E plays a significant role in DNA repair and radiation tolerance.
• This study highlights a novel mechanism for adaptation to extreme environmental conditions through gene transfer.