Section on Eukaryotic Transposable Elements, Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Nucleic Acids Res. 2013 Jan;41(2):775-89. doi: 10.1093/nar/gks1185. Epub 2012 Nov 27.
Transposable elements possess specific patterns of integration. The biological impact of these integration profiles is not well understood. Tf1, a long-terminal repeat retrotransposon in Schizosaccharomyces pombe, integrates into promoters with a preference for the promoters of stress response genes. To determine the biological significance of Tf1 integration, we took advantage of saturated maps of insertion activity and studied how integration at hot spots affected the expression of the adjacent genes. Our study revealed that Tf1 integration did not reduce gene expression. Importantly, the insertions activated the expression of 6 of 32 genes tested. We found that Tf1 increased gene expression by inserting enhancer activity. Interestingly, the enhancer activity of Tf1 could be limited by Abp1, a host surveillance factor that sequesters transposon sequences into structures containing histone deacetylases. We found the Tf1 promoter was activated by heat treatment and, remarkably, only genes that themselves were induced by heat could be activated by Tf1 integration, suggesting a synergy of Tf1 enhancer sequence with the stress response elements of target promoters. We propose that the integration preference of Tf1 for the promoters of stress response genes and the ability of Tf1 to enhance the expression of these genes co-evolved to promote the survival of cells under stress.
转座元件具有特定的整合模式。这些整合模式的生物学影响尚不清楚。Tf1 是一种存在于酿酒酵母中的长末端重复反转录转座子,它优先整合到应激反应基因的启动子中。为了确定 Tf1 整合的生物学意义,我们利用插入活性的饱和图谱,研究了热点处的整合如何影响相邻基因的表达。我们的研究表明,Tf1 整合不会降低基因表达。重要的是,插入激活了 32 个测试基因中的 6 个基因的表达。我们发现 Tf1 通过插入增强子活性来增加基因表达。有趣的是,Tf1 的增强子活性可以被 Abp1 限制,Abp1 是一种宿主监视因子,它将转座子序列隔离到含有组蛋白去乙酰化酶的结构中。我们发现 Tf1 启动子可以被热处理激活,而且引人注目的是,只有那些本身被热诱导的基因才能被 Tf1 整合激活,这表明 Tf1 增强子序列与靶启动子的应激反应元件之间存在协同作用。我们提出,Tf1 优先整合到应激反应基因的启动子上,以及 Tf1 增强这些基因表达的能力是共同进化的,以促进细胞在应激下的生存。