A genetic screen for improved plasmid segregation reveals a role for Rep20 in the interaction of Plasmodium falciparum chromosomes
A genetic screen for improved plasmid segregation reveals a role for Rep20 in the interaction of Plasmodium falciparum chromosomes
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DOI：
10.1093/emboj/21.5.1231
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发表时间：
2002-03-01
期刊：
影响因子：
11.4
通讯作者：
Crabb, BS
中科院分区：
文献类型：
--
作者：
O'Donnell, RA;Freitas, LH;Crabb, BS
引入人类疟疾寄生虫恶性疟原虫的细菌质粒复制良好，但在有丝分裂过程中分离不良。在本文中，我们筛选了一个随机的恶性疟原虫基因组文库，以确定克服这种分离缺陷的序列。使用这种方法，我们选择了具有独特的21 bp重复序列（称为Rep 20）的寄生虫。Rep 20是在所有恶性疟原虫染色体的亚端粒区域中发现的六种不同重复序列之一，但在其他真核生物或其他疟原虫中没有发现。使用多种方法，我们证明Rep 20序列通过促进子裂殖子之间的质粒分离而导致显著改善的附加型维持。我们发现，Rep 20（+），而不是Rep 20（-），质粒与末端染色体簇共定位，表明Rep 20介导质粒拴系到染色体，一种机制，解释了改进的分离表型。这项研究暗示了Rep 20在染色体末端的物理关联中的直接作用，这是一个促进末端定位的恶性疟原虫毒力基因产生多样性的过程。
Bacterial plasmids introduced into the human malaria parasite Plasmodium falciparum replicate well but are poorly segregated during mitosis. In this paper, we screened a random P. falciparum genomic library in order to identify sequences that overcome this segregation defect. Using this approach, we selected for parasites that harbor a unique 21 bp repeat sequence known as Rep20. Rep20 is one of six different repeats found in the subtelomeric regions of all P. falciparum chromosomes but which is not found in other eukaryotes or in other plasmodia. Using a number of approaches, we demonstrate that Rep20 sequences lead to dramatically improved episomal maintenance by promoting plasmid segregation between daughter merozoites. We show that Rep20(+), but not Rep20(-), plasmids co-localize with terminal chromosomal clusters, indicating that Rep20 mediates plasmid tethering to chromosomes, a mechanism that explains the improved segregation phenotype. This study implicates a direct role for Rep20 in the physical association of chromosome ends, which is a process that facilitates the generation of diversity in the terminally located P. falciparum virulence genes.