Telomeres are nucleoprotein complexes at the ends of chromosomes and are indispensable for the protection and lengthening of terminal DNA. Despite the evolutionarily conserved roles of telomeres, the telomeric double-strand DNA (dsDNA)-binding proteins have evolved rapidly. Here, we identified double-strand telomeric DNA-binding proteins (DTN-1 and DTN-2) in Caenorhabditis elegans as non-canonical telomeric dsDNA-binding proteins. DTN-1 and DTN-2 are paralogous proteins that have three putative MYB-like DNA-binding domains and bind to telomeric dsDNA in a sequence-specific manner. DTN-1 and DTN-2 form complexes with the single-strand telomeric DNA-binding proteins POT-1 and POT-2 and constitutively localize to telomeres. The dtn-1 and dtn-2 genes function redundantly, and their simultaneous deletion results in progressive germline mortality, which accompanies telomere hyper-elongation and chromosomal bridges. Our study suggests that DTN-1 and DTN-2 are core shelterin components in C. elegans telomeres that act as negative regulators of telomere length and are essential for germline immortality.

中文翻译：

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端粒双链 DNA 结合蛋白 DTN-1 和 DTN-2 确保秀丽隐杆线虫的种系永生

端粒是染色体末端的核蛋白复合物，对于末端DNA的保护和延长是必不可少的。尽管端粒在进化上具有保守的作用，但端粒双链 DNA (dsDNA) 结合蛋白已经迅速进化。在这里，我们将秀丽隐杆线虫中的双链端粒 DNA 结合蛋白（DTN-1 和 DTN-2）鉴定为非规范的端粒 dsDNA 结合蛋白。DTN-1 和 DTN-2 是具有三个推定的 MYB 样 DNA 结合结构域并以序列特异性方式与端粒 dsDNA 结合的旁系同源蛋白。DTN-1 和 DTN-2 与单链端粒 DNA 结合蛋白 POT-1 和 POT-2 形成复合物，并组成性定位于端粒。dtn-1 和 dtn-2 基因功能冗余，它们的同时缺失导致进行性生殖系死亡，它伴随着端粒超伸长和染色体桥。我们的研究表明，DTN-1 和 DTN-2 是秀丽隐杆线虫端粒中的核心遮蔽蛋白成分，它们作为端粒长度的负调节因子，对种系永生至关重要。