In plants, the small protein related to ubiquitin (RUB) modifies cullin (CUL) proteins in ubiquitin E3 ligases to allow for efficient transfer of ubiquitin to substrate proteins for degradation by the 26S proteasome. At the molecular level, the conjugation of RUB to individual CUL proteins is transient in nature, which aids in the stability of the cullins and adaptor proteins. Many changes in cellular processes occur within the plant upon exposure to light, including well-documented changes in the stability of individual proteins. However, overall activity of E3 ligases between dark- and light-grown seedlings has not been assessed in plants. In order to understand more about the activity of the protein degradation pathway, overall levels of RUB-modified CULs were measured in Arabidopsis thaliana seedlings growing in different light conditions. We found that light influenced the global levels of RUBylation on CULs, but not uniformly. Blue light had little effect on both Cul1 and Cul3 RUBylation levels. However, red light directed the increase in Cul3 RUBylation levels, but not Cul1. This red-light regulation of Cul3 was at least partially dependent on the activation of the phytochrome B signaling pathway. The results indicate that the RUBylation levels on individual CULs change in response to different light conditions, which enable plants to fine-tune their growth and development to the various light environments.

中文翻译：

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光调节拟南芥中单个库林蛋白的 RUBylation 水平

在植物中，与泛素相关的小蛋白 (RUB) 修饰泛素 E3 连接酶中的库林 (CUL) 蛋白，以允许泛素有效转移至底物蛋白，以便被 26S 蛋白酶体降解。在分子水平上，RUB 与单个 CUL 蛋白的结合本质上是短暂的，这有助于 cullins 和接头蛋白的稳定性。暴露在光下时，植物内的细胞过程会发生许多变化，包括有据可查的单个蛋白质稳定性的变化。然而，尚未在植物中评估深色和浅色幼苗之间 E3 连接酶的整体活性。为了更多地了解蛋白质降解途径的活性，在不同光照条件下生长的拟南芥幼苗中测量了 RUB 修饰的 CUL 的总体水平。我们发现光影响了 CUL 上 RUBylation 的全局水平，但不是统一的。蓝光对 Cul1 和 Cul3 RUBylation 水平几乎没有影响。然而，红光引导了 Cul3 RUBylation 水平的增加，而不是 Cul1。Cul3 的这种红光调节至少部分依赖于光敏色素 B 信号通路的激活。结果表明，单个 CUL 上的 RUBylation 水平会响应不同的光照条件而变化，这使植物能够根据各种光照环境微调其生长和发育。Cul3 的这种红光调节至少部分依赖于光敏色素 B 信号通路的激活。结果表明，单个 CUL 上的 RUBylation 水平会随着不同的光照条件而变化，这使植物能够根据各种光照环境微调它们的生长和发育。Cul3 的这种红光调节至少部分依赖于光敏色素 B 信号通路的激活。结果表明，单个 CUL 上的 RUBylation 水平会随着不同的光照条件而变化，这使植物能够根据各种光照环境微调它们的生长和发育。