Lotito Luca, Russo Alessandra, Bueno Susana, Chillemi Giovanni, Fogli Maria Vittoria, Capranico Giovanni
G Moruzzi Department of Biochemistry, University of Bologna, Bologna, Italy.
Eur J Pharmacol. 2009 Jan 28;603(1-3):29-36. doi: 10.1016/j.ejphar.2008.12.002. Epub 2008 Dec 9.
Topoisomerase I (Top1) is the specific target of the anticancer drug camptothecin (CPT) that interferes with enzyme activity promoting Top1-mediated DNA breaks and inhibition of DNA and RNA synthesis. To define the specific transcriptional response to CPT, we have determined the CPT-altered transcription profiles in yeast by using a relatively low concentration of the drug. CPT could alter global expression profiles only if a catalytically active Top1p was expressed in the cell, demonstrating that drug interference with Top1 was the sole trigger of the response. A total of 95 genes showed a statistically-significant alterations. Gene Ontology term analyses suggested that the cell response was mainly to the inhibition of nucleic acid synthesis and cell cycle progression. Promoter sequence analyses of the 22 up-regulated genes and expression studies in gene-deleted strains showed that the transcription factors, Swi4p and Mbp1p, mediate at least partially the transcriptional response to CPT. The MBP1 gene deletion abrogates a transient cell growth delay caused by CPT whereas the SWI4 gene deletion increases yeast resistance to CPT. Thus, the findings show that yeast cells have a highly selective and sensitive transcriptional response to CPT depending on SWI4 and MBP1 genes suggesting a complex regulation of cell cycle progression by the two factors in the presence of CPT.
拓扑异构酶I（Top1）是抗癌药物喜树碱（CPT）的特异性靶点，CPT会干扰酶活性，促进Top1介导的DNA断裂，并抑制DNA和RNA合成。为了确定对CPT的特异性转录反应，我们使用相对低浓度的该药物测定了酵母中CPT改变的转录谱。只有当细胞中表达有催化活性的Top1p时，CPT才能改变整体表达谱，这表明药物对Top1的干扰是反应的唯一触发因素。共有95个基因显示出具有统计学意义的改变。基因本体术语分析表明，细胞反应主要是对核酸合成抑制和细胞周期进程的反应。对22个上调基因的启动子序列分析以及在基因缺失菌株中的表达研究表明，转录因子Swi4p和Mbp1p至少部分介导了对CPT的转录反应。MBP1基因缺失消除了CPT引起的短暂细胞生长延迟，而SWI4基因缺失则增加了酵母对CPT的抗性。因此，这些发现表明酵母细胞对CPT具有高度选择性和敏感性的转录反应，这取决于SWI4和MBP1基因，提示在CPT存在的情况下，这两个因子对细胞周期进程进行复杂调控。
