Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA.
Department of Applied Biology and Chemical Technology, State Key Laboratory of Chirosciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China.
Sci Adv. 2020 Sep 18;6(38). doi: 10.1126/sciadv.abc4065. Print 2020 Sep.
Localization of Repressor Activator Protein 1 (RAP1) to the telomere is essential for its telomeric functions. RAP1 homologs either directly bind the duplex telomere DNA or interact with telomere-binding proteins. We find that RAP1 relies on a unique double-stranded DNA (dsDNA) binding activity to achieve this goal. causes human sleeping sickness and regularly switches its major surface antigen, variant surface glycoprotein (VSG), to evade the host immune response. VSGs are monoallelically expressed from subtelomeres, and RAP1 is essential for VSG regulation. We identify dsDNA and single-stranded DNA binding activities in RAP1, which require positively charged RKRRR residues that overlap with RAP1's nuclear localization signal in the MybLike domain. Both DNA binding activities are electrostatics-based and sequence nonspecific. The dsDNA binding activity can be substantially diminished by phosphorylation of two RKRRR-adjacent S residues and is essential for RAP1's telomere localization, VSG silencing, telomere integrity, and cell proliferation.
阻遏物激活蛋白 1（RAP1）在端粒上的定位对于其端粒功能至关重要。RAP1 同源物直接结合双链端粒 DNA 或与端粒结合蛋白相互作用。我们发现 RAP1 依赖于独特的双链 DNA（dsDNA）结合活性来实现这一目标。RAP1 是导致人类昏睡病的原因，它经常切换其主要表面抗原，变异表面糖蛋白（VSG），以逃避宿主的免疫反应。VSGs 从端粒下区单等位基因表达，而 RAP1 对于 VSG 的调控是必不可少的。我们在 RAP1 中鉴定出 dsDNA 和单链 DNA 结合活性，这需要正电荷的 RKRRR 残基，该残基与 MybLike 结构域中 RAP1 的核定位信号重叠。这两种 DNA 结合活性都是基于静电的，并且序列是非特异性的。dsDNA 结合活性可被两个 RKRRR 相邻 S 残基的磷酸化显著减弱，对于 RAP1 的端粒定位、VSG 沉默、端粒完整性和细胞增殖是必不可少的。
