A novel polyubiquitin structure in Cercozoa and Foraminifera: Evidence for a new eukaryotic supergroup
A novel polyubiquitin structure in Cercozoa and Foraminifera: Evidence for a new eukaryotic supergroup
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DOI：
10.1093/molbev/msg006
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发表时间：
2003-01-01
影响因子：
10.7
通讯作者：
Keeling, PJ
中科院分区：
文献类型：
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作者：
Archibald, JM;Longet, D;Keeling, PJ
泛素是一种由76个氨基酸组成的蛋白质，具有显著的进化保守性。泛素通过靶向蛋白质进行蛋白酶体介导的降解，在许多真核细胞过程中发挥重要作用。大多数泛素基因被发现为头-尾聚合物，其产物被后处理为泛素单体。我们已经表征了来自光合变形虫Chlorarachnion sp. CCMP 621（也称为Bigelowiella natans）的多聚泛素基因，并且发现它们偏离了典型的多聚泛素结构，在每个单体之间的连接处具有氨基酸插入，这表明该生物体中的多聚泛素加工在真核生物中是独特的。基因结构表明，加工可能会在插入的氨基末端切割单体。我们通过对其他几个真核生物组的多聚泛素基因进行测序，研究了插入的系统发育分布，发现它仅限于尾虫（包括Chlorarachnion，Lotharella，Cercomonas和Euglypha）和有孔虫（包括Reticulomyxa和Haynesina）。这一特征有力地表明，尾虫和有孔虫是近亲，并形成了一个新的真核生物的“超类群”。
Ubiquitin is a 76 amino acid protein with a remarkable degree of evolutionary conservation. Ubiquitin plays an essential role in a large number of eukaryotic cellular processes by targeting proteins for proteasome-mediated degradation. Most ubiquitin genes are found as head-to-tail polymers whose products are posttranslationally processed to ubiquitin monomers. We have characterized polyubuiquitin genes from the photosynthetic amoeboflagellate Chlorarachnion sp. CCMP 621 (also known as Bigelowiella natans) and found that they deviate from the canonical polyubiquitin structure in having an amino acid insertion at the junction between each monomer, suggesting that polyubiquitin processing in this organism is unique among eukaryotes. The gene structure indicates that processing likely cleaves monomers at the amino terminus of the insertion. We examined the phylogenetic distribution of the insertion by sequencing polyubiquitin genes from several other eukaryotic groups and found it to be confined to Cercozoa (including Chlorarachnion, Lotharella, Cercomonas, and Euglypha) and Foraminifera (including Reticulomyxa and Haynesina). This character strongly suggests that Cercozoa and Foraminifera are close relatives and form a new "supergroup" of eukaryotes.