ABSTRACT

ORANGE (OR) is a member of the DnaJ-like zinc finger domain-containing protein family, of which all orthologs share a highly conserved quadruple repeat of the CxxCxxxG signatures at their C-termini. Dual subcellular localization and different interacting partner proteins have been reported for OR. In plastids, OR interacts with phytoene synthase, the entry enzyme for carotenoid biosynthesis, to promote chromoplast biogenesis and carotenoid accumulation in non-pigmented tissues. In the nucleus, OR interacts with the eukaryotic release factor eRF1-2 to regulate cell elongation in the petiole, and with the transcription factor TCP14 to repress the expression of Early Light-Induced Proteins (ELIPs) and chloroplast biogenesis in de-etiolating cotyledons. In this study, we demonstrated the E2 ubiquitin-conjugating enzyme UBC19 as a new interacting partner of OR. The lysine⁵⁸ of OR was found to be ubiquitinated, and OR lost its nuclear localization and the capability in repressing ELIPs when lysine⁵⁸ was substituted by alanine. Our findings raised the possibility that the ubiquitination by UBC19 is essential for the nuclear localization of OR.

摘要

ORANGE (OR) 是 DnaJ 样锌指结构域蛋白家族的成员，其中所有直向同源物在其 C 端共享高度保守的 CxxCxxxG 特征四重重复。已经报道了 OR 的双亚细胞定位和不同的相互作用伙伴蛋白。在质体中，OR 与八氢番茄红素合成酶（类胡萝卜素生物合成的进入酶）相互作用，以促进非色素组织中的有色体生物发生和类胡萝卜素积累。在细胞核中，OR 与真核释放因子 eRF1-2 相互作用以调节叶柄中的细胞伸长，并与转录因子 TCP14 相互作用以抑制早期光诱导蛋白( ELIPs) 的表达) 和去黄化子叶中的叶绿体生物发生。在这项研究中，我们证明了 E2 泛素结合酶 UBC19 作为 OR 的新相互作用伙伴。发现 OR的赖氨酸⁵⁸被泛素化，当赖氨酸⁵⁸被丙氨酸取代时，OR 失去了其核定位和抑制ELIP的能力。我们的研究结果提出了一种可能性，即 UBC19 的泛素化对于 OR 的核定位是必不可少的。