Francis Malik Joseph, Roche Siobhan, Cho Michael Jeffrey, Beall Eileen, Min Bosun, Panganiban Ronaldo Paolo, Rio Donald C
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
Proc Natl Acad Sci U S A. 2016 Nov 15;113(46):13003-13008. doi: 10.1073/pnas.1613508113. Epub 2016 Oct 31.
In Drosophila, P-element transposition causes mutagenesis and genome instability during hybrid dysgenesis. The P-element 31-bp terminal inverted repeats (TIRs) contain sequences essential for transposase cleavage and have been implicated in DNA repair via protein-DNA interactions with cellular proteins. The identity and function of these cellular proteins were unknown. Biochemical characterization of proteins that bind the TIRs identified a heterodimeric basic leucine zipper (bZIP) complex between an uncharacterized protein that we termed "Inverted Repeat Binding Protein (IRBP) 18" and its partner Xrp1. The reconstituted IRBP18/Xrp1 heterodimer binds sequence-specifically to its dsDNA-binding site within the P-element TIRs. Genetic analyses implicate both proteins as critical for repair of DNA breaks following transposase cleavage in vivo. These results identify a cellular protein complex that binds an active mobile element and plays a more general role in maintaining genome stability.
在果蝇中，P 因子转座在杂种不育过程中会导致诱变和基因组不稳定。P 因子的 31 个碱基对的末端反向重复序列（TIRs）包含转座酶切割所必需的序列，并且通过与细胞蛋白的蛋白质-DNA 相互作用参与 DNA 修复。这些细胞蛋白的身份和功能尚不清楚。对结合 TIRs 的蛋白质进行生化特性分析，确定了一种异源二聚体碱性亮氨酸拉链（bZIP）复合物，该复合物存在于一种我们称为“反向重复结合蛋白（IRBP）18”的未鉴定蛋白与其伴侣 Xrp1 之间。重组的 IRBP18/Xrp1 异源二聚体序列特异性地结合其在 P 因子 TIRs 内的双链 DNA 结合位点。遗传分析表明这两种蛋白对于体内转座酶切割后 DNA 断裂的修复至关重要。这些结果鉴定出一种细胞蛋白复合物，它结合一个活跃的移动元件，并在维持基因组稳定性方面发挥更广泛的作用。
