Walther T C, Kennell J C
Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, USA.
Mol Cell. 1999 Aug;4(2):229-38. doi: 10.1016/s1097-2765(00)80370-6.
Diverse types of linear RNA and DNA autonomously replicating genetic elements exist in prokaryotic and eukaryotic hosts, yet linear elements that replicate by reverse transcription have not been identified. Here, we report the sequence and organization of two linear mitochondrial plasmids of the fungal plant pathogen F. oxysporum and the characterization of a plasmid-associated reverse transcriptase activity. Plasmids pFOXC2 and pFOXC3 are 1.9 kb in length and have a "clothespin" genomic structure, which includes a terminal hairpin and a telomere-like iteration of a 5 bp sequence at the other terminus. The retroplasmid replication cycle involves novel strategies for copying terminal sequences, which may provide clues concerning the origin of telomerase as well as the evolution of linear DNAs.
原核生物和真核生物宿主中存在多种类型的线性RNA和DNA自主复制遗传元件，但尚未鉴定出通过逆转录进行复制的线性元件。在此，我们报告了真菌植物病原菌尖孢镰刀菌（F. oxysporum）的两个线性线粒体质粒的序列和组织，以及一种与质粒相关的逆转录酶活性的特征。质粒pFOXC2和pFOXC3长度为1.9 kb，具有“衣夹”基因组结构，包括一个末端发夹结构和另一端一个5 bp序列的端粒样重复序列。逆转录质粒复制周期涉及复制末端序列的新策略，这可能为端粒酶的起源以及线性DNA的进化提供线索。
