Lauermann V, Boeke J D
Department of Molecular Biology and Genetics, School of Medicine, Johns Hopkins University, Baltmore, MD 21205, USA.
EMBO J. 1997 Nov 3;16(21):6603-12. doi: 10.1093/emboj/16.21.6603.
The yeast Ty1 LTR retrotransposon replicates by reverse transcription and integration; the process shows many similarities to the retroviral life cycle. However, we show that plus strand strong-stop DNA transfer in yeast Ty1 elements differs from the analogous retroviral process. By analysis of the native structure of the Ty1 primer binding site and by a series of manipulations of this region and assessment of the effects on retrotransposition, we show that primer binding site inheritance is not from the tRNA primer, which is inconsistent with classical retroviral models. This unusual inheritance pattern holds even when the Ty1 primer binding site is lengthened in order to be more retrovirus-like. Finally, the distantly related Ty3 element has an inheritance pattern like Ty1, indicating evolutionary conservation of the alternative pathway used by Ty1. Based on these results we arrive at a plus strand primer recycling model that explains Ty1 plus strand strong-stop DNA transfer and inheritance patterns in the primer binding site.
酵母Ty1长末端重复序列逆转录转座子通过逆转录和整合进行复制；该过程与逆转录病毒的生命周期有许多相似之处。然而，我们发现酵母Ty1元件中的正链强终止DNA转移不同于类似的逆转录病毒过程。通过分析Ty1引物结合位点的天然结构，并对该区域进行一系列操作以及评估对逆转录转座的影响，我们发现引物结合位点的遗传并非来自tRNA引物，这与经典的逆转录病毒模型不一致。即使将Ty1引物结合位点延长以使其更像逆转录病毒，这种不寻常的遗传模式仍然存在。最后，远缘相关的Ty3元件具有与Ty1相似的遗传模式，表明Ty1所使用的替代途径具有进化保守性。基于这些结果，我们得出了一个正链引物循环模型，该模型解释了Ty1正链强终止DNA转移和引物结合位点的遗传模式。
