Aranda-Anzaldo Armando
Laboratorio de Biología Molecular y Neurociencias, Facultad de Medicina, Universidad Autónoma del Estado de México, Paseo Tollocan y Jesús Carranza s/n, Toluca, 50180 Edo. Méx., México.
J Theor Biol. 2016 Mar 21;393:51-9. doi: 10.1016/j.jtbi.2016.01.005. Epub 2016 Jan 15.
Each mammalian chromosome is constituted by a DNA fiber of macroscopic length that needs to be fitted in a microscopic nucleus. The DNA fiber is subjected at physiological temperature to random thermal bending and looping that must be constrained so as achieve structural stability thus avoiding spontaneous rupturing of the fiber. Standard textbooks assume that chromatin proteins are primarily responsible for the packaging of DNA and so of its protection against spontaneous breakage. Yet the dynamic nature of the interactions between chromatin proteins and DNA is unlikely to provide the necessary long-term structural stability for the chromosomal DNA. On the other hand, longstanding evidence indicates that stable interactions between DNA and constituents of a nuclear compartment commonly known as the nuclear matrix organize the chromosomal DNA as a series of topologically constrained, supercoiled loops during interphase. This results in a primary level of DNA condensation and packaging within the nucleus, as well as in protection against spontaneous DNA breakage, independently of chromatin proteins which nevertheless increase and dynamically modulate the degree of DNA packaging and its role in the regulation of DNA function. Thus current evidence, presented hereunder, supports a model for the organization of the interphase chromosome as resilient system that satisfies the principles of structural tensegrity.
每个哺乳动物染色体都由宏观长度的DNA纤维构成，而这种DNA纤维需要被装入微观的细胞核中。在生理温度下，DNA纤维会受到随机的热弯曲和环化作用，必须对这些作用加以限制，以实现结构稳定性，从而避免纤维的自发断裂。标准教科书认为，染色质蛋白主要负责DNA的包装以及对其免受自发断裂的保护。然而，染色质蛋白与DNA之间相互作用的动态性质不太可能为染色体DNA提供必要的长期结构稳定性。另一方面，长期以来的证据表明，DNA与通常被称为核基质的核区室成分之间的稳定相互作用，在间期将染色体DNA组织成一系列拓扑受限的超螺旋环。这导致了细胞核内DNA凝聚和包装的初级水平，以及对DNA自发断裂的保护，这一过程独立于染色质蛋白，不过染色质蛋白会增加并动态调节DNA包装的程度及其在DNA功能调控中的作用。因此，如下所述的当前证据支持一种将间期染色体组织为满足结构张拉整体原理的弹性系统的模型。
