UC Santa Barbara

Damage from ultraviolet (UV) radiation was likely to be an important selection pressure during the origin of life. RNA is believed to have been central to the origin of life and might form the basis for simple synthetic cells. Although photodamage of DNA has been extensively studied, photodamage is highly dependent on local molecular context, and damage to functional RNAs has been relatively under-studied. We irradiated two fluorescent RNA aptamers and monitored the loss of activity, folding, and the kinetics of lesion accumulation. The loss of activity differed depending on the aptamer, with the Spinach2 aptamer retaining substantial activity after long exposure times. The binding pocket was particularly susceptible to damage, and melting of the duplex regions increased susceptibility; this is consistent with the view that duplex formation is protective. At the same time, susceptibility varied greatly depending on context, thus emphasizing the importance of studying many different RNAs to understand UV hardiness.