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首页> 外文学位 >Etude structurale du mode de liaison des proteines Whirly de plantes a l'ADN monocatenaire.
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Etude structurale du mode de liaison des proteines Whirly de plantes a l'ADN monocatenaire.

机译：植物中Whirly蛋白与单链DNA结合模式的结构研究。

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摘要

Plants must protect the integrity of three genomes located respectively in the nucleus, the chloroplasts and the mitochondria. Although DNA repair mechanisms in the nucleus are the subject of multiple studies, little attention has been paid to DNA repair mechanisms in chloroplasts and mitochondria. This is unfortunate since mutations in the chloroplast or the mitochondrial genome can lead to altered plant growth and development. Our laboratory has identified a new family of proteins, the Whirlies, whose members are located in plant mitochondria and chloroplasts. These proteins form tetramers that bind single-stranded DNA and play various roles associated with DNA metabolism. In Arabidopsis, two Whirly proteins maintain chloroplast genome stability. Whether or not these proteins are involved in DNA repair has so far not been investigated.;Keywords: Plant organelles, chloroplastic and mitochondrial genomes, DNA repair, DNA rearrangements mediated by very short repeated sequences, single-stranded DNA binding proteins, Whirly proteins, protein oligomerization, X-ray crystallography.;Our studies in Arabidopsis demonstrate that DNA double-strand breaks are repaired in both mitochondria and chloroplasts through a microhomology-mediated repair pathway and indicate that Whirly proteins affect this pathway. In particular, the role of Whirly proteins would be to promote accurate repair of organelle DNA by preventing the repair of DNA double-strand breaks by the microhomology-dependant pathway. To understand how Whirly proteins mediate this function, we solved the crystal structure of Whirly-DNA complexes. These structures show that Whirly proteins bind single-stranded DNA with low sequence specificity. The DNA is maintained in an extended conformation between the beta-sheets of adjacent protomers, thus preventing spurious annealing with a complementary strand. In turn, this prevents formation of DNA rearrangements and favors accurate DNA repair. We also show that upon binding long ssDNA sequences, Whirly proteins assemble into higher order structures, or hexamers of tetramers, thus forming spherical particles of twelve nanometers in diameter. We also demonstrate that a lysine residue conserved among plant Whirly proteins is important for the stability of these higher order structures as well as for cooperative binding to DNA and for DNA repair. Overall, our study elucidates some of the mechanisms of DNA repair in plant organelles as well as the roles of Whirly proteins in this process.
机译：植物必须保护分别位于细胞核，叶绿体和线粒体中的三个基因组的完整性。尽管细胞核中的DNA修复机制是多项研究的主题，但很少关注叶绿体和线粒体中的DNA修复机制。这是不幸的，因为叶绿体或线粒体基因组中的突变会导致植物生长和发育的改变。我们的实验室确定了一个新的蛋白质家族，即Whirlies，其成员位于植物线粒体和叶绿体中。这些蛋白质形成结合单链DNA的四聚体，并发挥与DNA代谢相关的各种作用。在拟南芥中，两种Whirly蛋白维持叶绿体基因组的稳定性。迄今为止，尚未研究这些蛋白质是否参与DNA修复。关键词：植物细胞器，叶绿体和线粒体基因组，DNA修复，由非常短的重复序列介导的DNA重排，单链DNA结合蛋白，Whirly蛋白，我们在拟南芥中的研究表明，线粒体和叶绿体中的DNA双链断裂均通过微同源介导的修复途径被修复，表明Whirly蛋白质会影响该途径。特别地，Whirly蛋白的作用是通过防止依赖微同源性途径的DNA双链断裂的修复来促进细胞器DNA的精确修复。为了了解Whirly蛋白如何介导此功能，我们解决了Whirly-DNA复合物的晶体结构。这些结构表明，Whirly蛋白以低序列特异性结合单链DNA。 DNA被保持在相邻的protomer的β-折叠之间的扩展构象中，从而防止了互补链的伪退火。反过来，这可以防止DNA重排的形成，并有助于精确的DNA修复。我们还表明，结合长的ssDNA序列后，Whirly蛋白组装成更高阶的结构或四聚体的六聚体，从而形成直径为12纳米的球形颗粒。我们还证明了植物Whirly蛋白之间保守的赖氨酸残基对于这些高级结构的稳定性以及与DNA的协同结合和DNA修复非常重要。总体而言，我们的研究阐明了植物细胞器中DNA修复的一些机制，以及Whirly蛋白在此过程中的作用。

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  • 作者

    Cappadocia, Laurent.;

  • 作者单位

    Universite de Montreal (Canada).;

  • 授予单位 Universite de Montreal (Canada).;
  • 学科 Chemistry Biochemistry.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 232 p.
  • 总页数 232
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 肿瘤学;
  • 关键词

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