Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI-CONICET), Universidad Nacional de Rosario, Rosario, Argentina.
PLoS One. 2013 Aug 28;8(8):e73104. doi: 10.1371/journal.pone.0073104. eCollection 2013.
Protein ubiquitination leading to degradation by the proteasome is an important mechanism in regulating key cellular functions. Protein ubiquitination is carried out by a three step process involving ubiquitin (Ub) activation by a E1 enzyme, the transfer of Ub to a protein E2, finally an ubiquitin ligase E3 catalyzes the transfer of the Ub peptide to an acceptor protein. The E3 component is responsible for the specific recognition of the target, making the unveiling of E3 components essential to understand the mechanisms regulating fundamental cell processes through the protein degradation pathways. The Arabidopsis thaliana seven in absentia-like 7 (AtSINAL7) gene encodes for a protein with characteristics from a C3HC4-type E3 ubiquitin ligase. We demonstrate here that AtSINAL7 protein is indeed an E3 protein ligase based on the self-ubiquitination in vitro assay. This activity is dependent of the presence of a Lys residue in position 124. We also found that higher AtSINAL7 transcript levels are present in tissues undergoing active cell division during floral development. An interesting observation is the circadian expression pattern of AtSINAL7 mRNA in floral buds. Furthermore, UV-B irradiation induces the expression of this transcript indicating that AtSINAL7 may be involved in a wide range of different cell processes.
蛋白质泛素化导致蛋白酶体降解是调节细胞关键功能的重要机制。蛋白质泛素化是通过三步过程完成的，涉及泛素（Ub）由 E1 酶激活，Ub 转移到蛋白 E2，最后泛素连接酶 E3 催化 Ub 肽转移到受体蛋白。E3 组件负责靶蛋白的特异性识别，因此揭示 E3 组件对于通过蛋白降解途径理解调节基本细胞过程的机制至关重要。拟南芥七缺素蛋白 7（AtSINAL7）基因编码具有 C3HC4 型 E3 泛素连接酶特征的蛋白。我们在此证明，AtSINAL7 蛋白确实是一种 E3 蛋白连接酶，这是基于体外自我泛素化测定。这种活性依赖于位置 124 处赖氨酸残基的存在。我们还发现，在花发育过程中组织进行活跃的细胞分裂时，AtSINAL7 的转录本水平更高。一个有趣的观察结果是花芽中 AtSINAL7 mRNA 的昼夜表达模式。此外，UV-B 辐射诱导该转录本的表达，表明 AtSINAL7 可能参与广泛的不同细胞过程。
