Moon Yoon-Jung, Kim Seung Il, Chung Young-Ho
Division of Life Science, Korea Basic Science Institute, Daejeon 305-806, Korea.
Int J Mol Sci. 2012 Dec 3;13(12):16303-32. doi: 10.3390/ijms131216303.
Ultraviolet (UV) radiation can cause stresses or act as a photoregulatory signal depending on its wavelengths and fluence rates. Although the most harmful effects of UV on living cells are generally attributed to UV-B radiation, UV-A radiation can also affect many aspects of cellular processes. In cyanobacteria, most studies have concentrated on the damaging effect of UV and defense mechanisms to withstand UV stress. However, little is known about the activation mechanism of signaling components or their pathways which are implicated in the process following UV irradiation. Motile cyanobacteria use a very precise negative phototaxis signaling system to move away from high levels of solar radiation, which is an effective escape mechanism to avoid the detrimental effects of UV radiation. Recently, two different UV-A-induced signaling systems for regulating cyanobacterial phototaxis were characterized at the photophysiological and molecular levels. Here, we review the current understanding of the UV-A mediated signaling pathways in the context of the UV-A perception mechanism, early signaling components, and negative phototactic responses. In addition, increasing evidences supporting a role of pterins in response to UV radiation are discussed. We outline the effect of UV-induced cell damage, associated signaling molecules, and programmed cell death under UV-mediated oxidative stress.
紫外线（UV）辐射根据其波长和通量率可造成压力或充当光调节信号。虽然紫外线对活细胞最有害的影响通常归因于UV-B辐射，但UV-A辐射也会影响细胞过程的许多方面。在蓝细菌中，大多数研究集中于紫外线的破坏作用以及抵御紫外线压力的防御机制。然而，对于紫外线照射后过程中涉及的信号成分或其途径的激活机制知之甚少。运动型蓝细菌利用非常精确的负趋光性信号系统远离高强度的太阳辐射，这是一种有效的逃避机制，可避免紫外线辐射的有害影响。最近，在光生理和分子水平上鉴定了两种不同的UV-A诱导的调节蓝细菌趋光性的信号系统。在此，我们结合UV-A感知机制、早期信号成分和负趋光反应，综述目前对UV-A介导的信号通路的理解。此外，还讨论了越来越多支持蝶呤在响应紫外线辐射中起作用的证据。我们概述了紫外线诱导的细胞损伤、相关信号分子以及紫外线介导的氧化应激下的程序性细胞死亡的影响。
