Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland.
Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland.
Biol Chem. 2018 Apr 25;399(5):467-484. doi: 10.1515/hsz-2017-0251.
FK506-binding proteins (FKBPs) belong to a distinct class of immunophilins that interact with immunosuppressants. They use their peptidyl-prolyl isomerase (PPIase) activity to catalyze the cis-trans conversion of prolyl bonds in proteins during protein-folding events. FKBPs also act as a unique group of chaperones. The Drosophila melanogaster peptidyl-prolyl cis-trans isomerase FK506-binding protein of 39 kDa (FKBP39) is thought to act as a transcriptional modulator of gene expression in 20-hydroxyecdysone and juvenile hormone signal transduction. The aim of this study was to analyze the molecular determinants responsible for the subcellular distribution of an FKBP39-yellow fluorescent protein (YFP) fusion construct (YFP-FKBP39). We found that YFP-FKBP39 was predominantly nucleolar. To identify the nuclear localization signal (NLS), a series of YFP-tagged FKBP39 deletion mutants were prepared and examined in vivo. The identified NLS signal is located in a basic domain. Detailed mutagenesis studies revealed that residues K188 and K191 are crucial for the nuclear targeting of FKBP39 and its nucleoplasmin-like (NPL) domain contains the sequence that controls the nucleolar-specific translocation of the protein. These results show that FKBP39 possesses a specific NLS in close proximity to a putative helix-turn-helix (HTH) motif and FKBP39 may bind DNA in vivo and in vitro.
FK506 结合蛋白（FKBP）属于免疫亲和素的一个独特类别，与免疫抑制剂相互作用。它们利用其肽基脯氨酰顺反异构酶（PPIase）活性，在蛋白质折叠事件中催化蛋白质中脯氨酸键的顺反转换。FKBP 还充当独特的一组伴侣。黑腹果蝇的肽基脯氨酰顺反异构酶 FK506 结合蛋白 39 kDa（FKBP39）被认为是 20-羟蜕皮激素和保幼激素信号转导中基因表达的转录调节剂。本研究旨在分析负责 FKBP39-黄色荧光蛋白（YFP）融合构建体（YFP-FKBP39）亚细胞分布的分子决定因素。我们发现 YFP-FKBP39 主要位于核仁。为了鉴定核定位信号（NLS），制备了一系列 YFP 标记的 FKBP39 缺失突变体，并在体内进行了检查。鉴定的 NLS 信号位于碱性结构域中。详细的诱变研究表明，残基 K188 和 K191 对于 FKBP39 的核靶向及其核质蛋白样（NPL）结构域至关重要，该结构域包含控制蛋白质核仁特异性易位的序列。这些结果表明，FKBP39 在接近假定的螺旋-转角-螺旋（HTH）基序的位置具有特定的 NLS，并且 FKBP39 可能在体内和体外结合 DNA。
