Increased sensitivity to gamma irradiation in bacteria lacking protein HU

Area of Science:

• Microbiology
• Molecular Biology
• Radiation Biology

Background:

• The heterodimeric HU protein from Escherichia coli is a small DNA-binding protein associated with the bacterial nucleoid.
• HU shares properties with histones and HMG proteins, playing pleiotropic roles in DNA replication, cell division, and transposition.
• Its specific role in DNA repair, particularly against radiation damage, is not fully elucidated.

Purpose of the Study:

• To investigate the role of the HU protein in bacterial response to gamma irradiation.
• To determine if the absence of HU protein leads to increased sensitivity to DNA damage.
• To elucidate the mechanism by which HU protein influences DNA repair.

Main Methods:

• Generating and characterizing an Escherichia coli hupAB double mutant lacking HU protein.
• Assessing the survival rates of wild-type and mutant bacteria after gamma irradiation.
• Analyzing the expression of SOS repair genes in the presence and absence of HU protein.
• Conducting in vitro studies to examine HU protein's effect on DNA cleavage.

Main Results:

• Bacteria lacking HU protein exhibit extreme sensitivity to gamma irradiation.
• Expression of either HU subunit in the hupAB double mutant nearly restores normal survival rates.
• The sensitivity is directly attributed to the absence of HU protein, not secondary mutations or SOS repair system modifications.
• In vitro studies suggest HU protein protects DNA against gamma-ray-induced cleavage.

Conclusions:

• The HU protein is essential for bacterial survival under gamma irradiation stress.
• HU protein plays a critical role in protecting DNA from radiation damage.
• HU protein's function in DNA repair is independent of SOS gene induction.