Kim Sang-Hoon, Kim Hani, Chung Sunglan, Lee Jae-Hoon
Department of Biology Education, Pusan National University, Busan 46241, South Korea.
Underwood International College, Yonsei University, Seoul 03722, South Korea.
Biochem Biophys Res Commun. 2017 Sep 16;491(2):285-290. doi: 10.1016/j.bbrc.2017.07.110. Epub 2017 Jul 21.
Although DWD HYPERSENSITIVE TO UV-B 1 (DHU1) is reported to be a negative regulator in UV-B mediated cellular responses, its detailed role in UV-B signaling is still elusive. To further understand the action mechanism of DHU1 in UV-B response, physical and genetic interactions of DHU1 with various UV-B signaling components were investigated. Yeast two hybrid assay results suggested that DHU1 directly interacts with COP1 and RUP1, implying a functional connection with both COP1 and RUP1. In spite of the physical association between DHU1 and COP1, loss of DHU1 did not affect protein stability of COP1. Epistatic analysis showed that the functional loss of both DHU1 and UVR8 leads to alleviation of UV-B hypersensitivity displayed in dhu1-1. Moreover, phenotypic studies with dhu1-1 cop1-6 and dhu1-1 hy5-215 revealed that COP1 and HY5 are epistatic to DHU1, indicating that UV-B hypersensitivity of dhu1-1 requires both COP1 and HY5. In the case of dhu1-1 rup1-1, UV-B responsiveness was similar to that of both dhu1-1 and rup1-1, implying that DHU1 and RUP1 are required for each other's function. Collectively, these results show that the role of DHU1 as a negative regulator in UV-B response may be derived from its direct interaction with COP1 by sequestering COP1 from the active UVR8-COP1 complex, resulting in a decrease in the COP1 population that positively participates in UV-B signaling together with UVR8. Furthermore, this inhibitory role of DHU1 in UV-B signaling is likely to be functionally connected to RUP1. This study will serve as a platform to further understand more detailed action mechanism of DHU1 in UV-B response and DHU1-mediated core UV-B signaling in Arabidopsis.
尽管据报道DWD紫外线B超敏反应1（DHU1）是紫外线B介导的细胞反应中的负调节因子，但其在紫外线B信号传导中的具体作用仍不清楚。为了进一步了解DHU1在紫外线B反应中的作用机制，研究了DHU1与各种紫外线B信号成分的物理和遗传相互作用。酵母双杂交试验结果表明，DHU1直接与COP1和RUP1相互作用，这意味着它与COP1和RUP1都存在功能联系。尽管DHU1与COP1之间存在物理关联，但DHU1的缺失并不影响COP1的蛋白质稳定性。上位性分析表明，DHU1和UVR8的功能丧失都会导致dhu1-1中紫外线B超敏反应的减轻。此外，对dhu1-1 cop1-6和dhu1-1 hy5-215的表型研究表明，COP1和HY5对DHU1具有上位性，这表明dhu1-1的紫外线B超敏反应需要COP1和HY5。在dhu1-1 rup1-1的情况下，紫外线B反应性与dhu1-1和rup1-1相似，这意味着DHU1和RUP1相互之间的功能是必需的。总的来说，这些结果表明，DHU1作为紫外线B反应中的负调节因子，其作用可能源于它与COP1的直接相互作用，通过将COP1从活性UVR8-COP1复合物中隔离出来，导致与UVR8一起积极参与紫外线B信号传导的COP1数量减少。此外，DHU1在紫外线B信号传导中的这种抑制作用可能在功能上与RUP1相关。这项研究将为进一步了解DHU1在拟南芥紫外线B反应中的更详细作用机制以及DHU1介导的核心紫外线B信号传导提供一个平台。
