期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：1
页码：18-20
DOI：10.1073/pnas.1920496117
出版社：The National Academy of Sciences of the United States of America
摘要：Trypanosoma is a genus of single-cell eukaryote organisms—parasites living in the bloodstream (or sometimes inside cells) of humans or other mammals and causing a number of serious diseases (such as Leishmaniasis, African trypanosomiasis [sleeping sickness], American trypanosomiasis [Chagas disease], and others). In most cases, they are transmitted by blood-feeding invertebrates, such as flies or mosquitos. They are also called kinetoplastids, because their major distinguishing feature is a subcellular structure known as the kinetoplast—their form of mitochondrial DNA. Truly surprising at first glance, the kinetoplast is a sort of a chainmail composed of thousands of concatenated DNA rings. While a lot is known about kinetoplasts’ biology, Klotz et al. (1) in PNAS offer a fresh view, abstracting from kinetoplast biological function and considering it as a peculiar material. Kinetoplasts were known to biologists a long time ago, but their structure came to light only starting around 1970 (see, e.g., review in ref. 2 and references therein). Interestingly, several related developments happened at about the same time. Perhaps unbeknown to one another, Vinograd and Hudson (3) observed a simple DNA catenane in human HeLa cell mitochondria; Sauvage and coworkers (4) invented protocols for chemical synthesis of molecular catenanes; and de Gennes (5), thinking of possible polymer gel structures, came up with the idea of the so-called olympic gel—a macroscopic network of concatenated ring polymers (ref. 5, section 5.1.2). The kinetoplast is actually just like an olympic gel, but more subtle. It consists of covalently closed (but, surprisingly, not supercoiled) DNA rings of 2 distinct types, minicircles and maxicircles. There are typically up to 10,000 minicircles, each about 0.5 to 3 kbp, and a few dozen maxicircles, each about 20 to 50 kbp. To place these numbers in context, persistence length of dsDNA is about 50 nm, or 150 bp, so maxicircles.
