Joseph Soumya, Kwan Ann H, Stokes Philippa H, Mackay Joel P, Cubeddu Liza, Matthews Jacqueline M
School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia.
School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia; School of Science and Health, University of Western Sydney, Campbelltown, NSW Australia.
PLoS One. 2014 Oct 13;9(10):e109108. doi: 10.1371/journal.pone.0109108. eCollection 2014.
LIM-domain only protein 4 (LMO4) is a widely expressed protein with important roles in embryonic development and breast cancer. It has been reported to bind many partners, including the transcription factor Deformed epidermal autoregulatory factor-1 (DEAF1), with which LMO4 shares many biological parallels. We used yeast two-hybrid assays to show that DEAF1 binds both LIM domains of LMO4 and that DEAF1 binds the same face on LMO4 as two other LMO4-binding partners, namely LIM domain binding protein 1 (LDB1) and C-terminal binding protein interacting protein (CtIP/RBBP8). Mutagenic screening analysed by the same method, indicates that the key residues in the interaction lie in LMO4LIM2 and the N-terminal half of the LMO4-binding domain in DEAF1. We generated a stable LMO4LIM2-DEAF1 complex and determined the solution structure of that complex. Although the LMO4-binding domain from DEAF1 is intrinsically disordered, it becomes structured on binding. The structure confirms that LDB1, CtIP and DEAF1 all bind to the same face on LMO4. LMO4 appears to form a hub in protein-protein interaction networks, linking numerous pathways within cells. Competitive binding for LMO4 therefore most likely provides a level of regulation between those different pathways.
仅含LIM结构域蛋白4（LMO4）是一种广泛表达的蛋白，在胚胎发育和乳腺癌中发挥重要作用。据报道，它能与许多蛋白结合，包括转录因子变形表皮自调节因子1（DEAF1），LMO4与DEAF1有许多生物学上的相似之处。我们利用酵母双杂交实验表明，DEAF1能与LMO4的两个LIM结构域结合，并且DEAF1与LMO4结合的面和另外两个与LMO4结合的蛋白伴侣相同，即LIM结构域结合蛋白1（LDB1）和C末端结合蛋白相互作用蛋白（CtIP/RBBP8）。通过相同方法进行的诱变筛选表明，相互作用中的关键残基位于LMO4的LIM2结构域以及DEAF1中LMO4结合结构域的N端一半区域。我们生成了稳定的LMO4LIM2 - DEAF1复合物，并确定了该复合物的溶液结构。尽管DEAF1的LMO4结合结构域本身是无序的，但结合后会形成有序结构。该结构证实LDB1、CtIP和DEAF1都与LMO4的同一面结合。LMO4似乎在蛋白质 - 蛋白质相互作用网络中形成了一个枢纽，连接细胞内的众多信号通路。因此，对LMO4的竞争性结合很可能在这些不同信号通路之间提供了一定程度的调控。
