Department of Biology, Boston University, Boston, MA, USA.
Commun Biol. 2021 Dec 16;4(1):1404. doi: 10.1038/s42003-021-02924-2.
We provide a functional characterization of transcription factor NF-κB in protists and provide information about the evolution and diversification of this biologically important protein. We characterized NF-κB in two protists using phylogenetic, cellular, and biochemical techniques. NF-κB of the holozoan Capsaspora owczarzaki (Co) has an N-terminal DNA-binding domain and a C-terminal Ankyrin repeat (ANK) domain, and its DNA-binding specificity is more similar to metazoan NF-κB proteins than to Rel proteins. Removal of the ANK domain allows Co-NF-κB to enter the nucleus, bind DNA, and activate transcription. However, C-terminal processing of Co-NF-κB is not induced by IκB kinases in human cells. Overexpressed Co-NF-κB localizes to the cytoplasm in Co cells. Co-NF-κB mRNA and DNA-binding levels differ across three Capsaspora life stages. RNA-sequencing and GO analyses identify possible gene targets of Co-NF-κB. Three NF-κB-like proteins from the choanoflagellate Acanthoeca spectabilis (As) contain conserved Rel Homology domain sequences, but lack C-terminal ANK repeats. All three As-NF-κB proteins constitutively enter the nucleus of cells, but differ in their DNA-binding abilities, transcriptional activation activities, and dimerization properties. These results provide a basis for understanding the evolutionary origins of this key transcription factor and could have implications for the origins of regulated immunity in higher taxa.
我们对原生动物中的转录因子 NF-κB 进行了功能表征，并提供了有关该生物重要蛋白的进化和多样化的信息。我们使用系统发育、细胞和生化技术对两种原生动物中的 NF-κB 进行了表征。全动物门的Capsaspora owczarzaki（Co）的 NF-κB 具有 N 端 DNA 结合域和 C 端 Ankyrin 重复（ANK）域，其 DNA 结合特异性与后生动物 NF-κB 蛋白更相似，而与 Rel 蛋白更相似。ANK 域的缺失允许 Co-NF-κB 进入细胞核，结合 DNA 并激活转录。然而，人类细胞中的 IκB 激酶不会诱导 Co-NF-κB 的 C 端加工。在 Co 细胞中，过表达的 Co-NF-κB 定位于细胞质中。Co-NF-κB 的 mRNA 和 DNA 结合水平在三个 Capsaspora 生命阶段存在差异。RNA-seq 和 GO 分析确定了 Co-NF-κB 的可能基因靶标。来自领鞭毛目原生动物 Acanthoeca spectabilis（As）的三种 NF-κB 样蛋白含有保守的 Rel Homology 结构域序列，但缺乏 C 端 ANK 重复序列。所有三种 As-NF-κB 蛋白都持续进入细胞的细胞核，但在 DNA 结合能力、转录激活活性和二聚化特性方面存在差异。这些结果为理解这一关键转录因子的进化起源提供了基础，并可能对高等分类群中调节免疫的起源产生影响。
