Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture, Chinese Academy of Agricultural Science, Beijing 100081, China.
Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100080, China.
Biochim Biophys Acta Gene Regul Mech. 2018 Aug;1861(8):743-751. doi: 10.1016/j.bbagrm.2018.07.002. Epub 2018 Jul 21.
Fertilization requires decondensation of promatine-condensed sperm chromatin, a dynamic process serving as an attractive system for the study of chromatin reprogramming. Nucleoplasmin is a key factor in regulating nucleosome assembly as a chaperone during fertilization process. However, knowledge on nucleoplasmin in chromatin formation remains elusive. Herein, magnetic tweezers (MT) and a chromatin assembly system were used to study the nucleoplasmin-mediated DNA decondensation/condensation at the single-molecular level in vitro. We found that protamine induces DNA condensation in a stepwise manner. Once DNA was condensed, nucleoplasmin, polyglutamic acid, and RNA could remove protamine from the DNA at different rates. The affinity binding of the different polyanions with protamine suggests chaperone-mediated chromatin decondensation activity occurs through protein-protein interactions. After decondensation, both RNA and polyglutamic acid prevented the transfer of histones onto the naked DNA. In contrast, nucleoplasmin is able to assist the histone transfer process, even though it carries the same negative charge as RNA and polyglutamic acid. These observations imply that the chaperone effects of nucleoplasmin during the decondensation/condensation process may be driven by specific spatial configuration of its acidic pentamer structure, rather than by electrostatic interaction. Our findings offer a novel molecular understanding of nucleoplasmin in sperm chromatin decondensation and subsequent developmental chromatin reprogramming at individual molecular level.
受精需要使精子染色质解凝聚，这是一个动态过程，可作为染色质重编程的研究系统。核质素是在受精过程中作为伴侣蛋白调节核小体组装的关键因素。然而，关于染色质形成中的核质素的知识仍然难以捉摸。在此，我们使用磁镊（MT）和染色质组装系统在体外的单分子水平上研究了核质素介导的 DNA 解凝聚/凝聚。我们发现鱼精蛋白以逐步的方式诱导 DNA 凝聚。一旦 DNA 被浓缩，核质素、多聚谷氨酸和 RNA 可以以不同的速率从 DNA 上去除鱼精蛋白。不同多阴离子与鱼精蛋白的亲和结合表明，伴侣蛋白介导的染色质解凝聚活性是通过蛋白-蛋白相互作用发生的。解凝聚后，RNA 和多聚谷氨酸都阻止组蛋白转移到裸露的 DNA 上。相比之下，核质素能够辅助组蛋白转移过程，尽管它携带与 RNA 和多聚谷氨酸相同的负电荷。这些观察结果表明，核质素在解凝聚/凝聚过程中的伴侣效应可能是由其酸性五聚体结构的特定空间构象驱动的，而不是由静电相互作用驱动的。我们的发现为精子染色质解凝聚和随后的个体分子水平上的发育性染色质重编程中核质素提供了新的分子理解。
