Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria; Temasek Lifesciences Laboratory, 1 Research Link, National University of Singapore, 117604 Singapore, Singapore; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543 Singapore, Singapore.
Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria; Temasek Lifesciences Laboratory, 1 Research Link, National University of Singapore, 117604 Singapore, Singapore.
Mol Plant. 2018 Aug 6;11(8):1038-1052. doi: 10.1016/j.molp.2018.05.004. Epub 2018 May 21.
Heterochromatin Protein 1 (HP1) is a major regulator of chromatin structure and function. In animals, the network of proteins interacting with HP1 is mainly associated with constitutive heterochromatin marked by H3K9me3. HP1 physically interacts with the putative ortholog of the SNF2 chromatin remodeler ATRX, which controls deposition of histone variant H3.3 in mammals. In this study, we show that the Arabidopsis thaliana ortholog of ATRX participates in H3.3 deposition and possesses specific conserved domains in plants. We found that plant Like HP1 (LHP1) protein interacts with ATRX through domains that evolved specifically in land plant ancestors. Loss of ATRX function in Arabidopsis affects the expression of a limited subset of genes controlled by PRC2 (POLYCOMB REPRESSIVE COMPLEX 2), including the flowering time regulator FLC. The function of ATRX in regulation of flowering time requires novel LHP1-interacting domain and ATPase activity of the ATRX SNF2 helicase domain. Taken together, these results suggest that distinct evolutionary pathways led to the interaction between ATRX and HP1 in mammals and its counterpart LHP1 in plants, resulting in distinct modes of transcriptional regulation.
异染色质蛋白 1（HP1）是染色质结构和功能的主要调节剂。在动物中，与 HP1 相互作用的蛋白质网络主要与 H3K9me3 标记的组成性异染色质有关。HP1 与假定的 SNF2 染色质重塑因子 ATRX 的同源物物理相互作用，该蛋白控制组蛋白变体 H3.3 在哺乳动物中的沉积。在这项研究中，我们表明 ATRX 的拟南芥同源物参与 H3.3 的沉积，并在植物中具有特定的保守结构域。我们发现植物样 HP1（LHP1）蛋白通过在陆地植物祖先中特异性进化的结构域与 ATRX 相互作用。拟南芥中 ATRX 功能的丧失会影响受 PRC2（多梳抑制复合物 2）控制的有限数量基因的表达，包括开花时间调节剂 FLC。ATRX 在调节开花时间中的功能需要新型的 LHP1 相互作用结构域和 ATRX SNF2 解旋酶结构域的 ATP 酶活性。综上所述，这些结果表明，哺乳动物中的 ATRX 和 HP1 及其在植物中的对应物 LHP1 之间的相互作用是通过不同的进化途径形成的，导致了不同的转录调控模式。
