MR (Mre11-Rad50) complex in Giardia duodenalis: In vitro characterization and its response upon DNA damage

Area of Science:

• Molecular Biology
• Parasitology
• Genetics

Background:

• Giardia duodenalis is a significant protozoan parasite.
• DNA double-strand break (DSB) repair is vital for genomic stability.
• Homologous recombination is a key DSB repair pathway involving the Mre11 complex.

Purpose of the Study:

• To clone, express, and characterize giardial Mre11 (GdMre11) and Rad50 (GdRad50).
• To investigate the DNA binding, catalytic activities, and structural features of GdMre11 and GdRad50.
• To examine the expression and localization of giardial mre11 and rad50 genes/proteins following ionizing radiation.

Main Methods:

• Cloning and recombinant expression of GdMre11 and GdRad50.
• Biochemical assays to determine DNA binding and enzymatic activities (exonuclease and ATPase).
• Bioinformatic analysis for structural prediction.
• Quantitative analysis of gene and protein expression post-gamma irradiation.
• Subcellular localization studies using microscopy.

Main Results:

• Purified recombinant GdMre11 and GdRad50 bind DNA.
• GdMre11 exhibits 3'-5' exonuclease activity, dependent on a conserved Mn(2+) binding pocket.
• GdRad50 possesses ATPase activity.
• Giardial mre11 and rad50 transcripts increased 1-2 hours post-irradiation, with protein levels rising significantly at 4 hours.
• GdMre11 and GdRad50 proteins are localized in the nucleus before and after irradiation.

Conclusions:

• GdMre11 and GdRad50 are functional components of the Mre11 complex in Giardia duodenalis.
• The proteins possess conserved catalytic activities essential for DNA repair.
• Increased expression and nuclear localization post-irradiation suggest their involvement in the DNA damage response pathway in Giardia.