Garfinkel David J, Stefanisko Karen M, Nyswaner Katherine M, Moore Sharon P, Oh Jangsuk, Hughes Stephen H
National Cancer Institute, P.O. Box B, Frederick, MD 21702-1201, USA.
J Virol. 2006 Dec;80(24):11920-34. doi: 10.1128/JVI.01483-06. Epub 2006 Sep 27.
Despite their evolutionary distance, the Saccharomyces cerevisiae retrotransposon Ty1 and retroviruses use similar strategies for replication, integration, and interactions with their hosts. Here we examine the formation of circular Ty1 DNA, which is comparable to the dead-end circular products that arise during retroviral infection. Appreciable levels of circular Ty1 DNA are present with one-long terminal repeat (LTR) circles and deleted circles comprising major classes, while two-LTR circles are enriched when integration is defective. One-LTR circles persist when homologous recombination pathways are blocked by mutation, suggesting that they result from reverse transcription. Ty1 autointegration events readily occur, and many are coincident with and dependent upon DNA flap structures that result from DNA synthesis initiated at the central polypurine tract. These results suggest that Ty1-specific mechanisms minimize copy number and raise the possibility that special DNA structures are a targeting determinant.
尽管酿酒酵母逆转座子Ty1与逆转录病毒在进化上距离较远，但它们在复制、整合以及与宿主的相互作用方面采用了相似的策略。在此，我们研究了环状Ty1 DNA的形成，其与逆转录病毒感染过程中产生的终末环状产物类似。相当数量的环状Ty1 DNA以单长末端重复（LTR）环和缺失环为主要类型存在，而当整合存在缺陷时，双LTR环会富集。当同源重组途径因突变而受阻时，单LTR环依然存在，这表明它们是逆转录的产物。Ty1自整合事件很容易发生，并且许多事件与由中央多聚嘌呤 tract起始的DNA合成所产生的DNA瓣状结构同时出现并依赖于此结构。这些结果表明，Ty1特异性机制使拷贝数最小化，并增加了特殊DNA结构是靶向决定因素的可能性。
