UV-induced DNA damage and repair: A cyanobacterial perspective

Cyanobacteria are ancient prokaryotic photoautotrophs which are considered as ancestor of chloroplast, having ability of oxygen evolution and are major biomass producers in both terrestrial as well as aquatic ecosystems. In recent years, their importance as bio-machinery for production of value added products have been established. In process of colonization of diverse habitats on Earth, cyanobacteria are exposed to several environmental stresses including ultraviolet radiation which results in DNA damage. Hence, applied as well as basic research should focus on better understanding of “repair systems” in cyanobacteria. One of the important repair mechanisms is photoreactivation which is found in cyanobacteria and utilizes enzyme “photolyase” for reverting modified bases into normal form. Other repair mechanisms include excision repair i.e. base excision repair (BER) and nucleotide excision repair (NER) in which enzymes such as polymerase, glycosylase and nuclease play important role. Furthermore, mechanisms such as recombinational repair and SOS repair are also important and if the damage is not repairable, apoptosis or programmed cell death is the final step to prevent the entry of damaged DNA in next generation. These mechanisms are not well studied in cyanobacteria and these studies are still in their infancy stage. Few experimental and in silico studied have showed the possible presence of certain genes in cyanobacteria responsible for DNA damage repair. Therefore, for optimum utilization of cyanobacterial system in industrial, biotechnological and pharmaceutical sectors better understanding of their repair system is needed.