Eloy Nubia Barbosa, Coppens Frederik, Beemster Gerrit T S, Hemerly Adriana Silva, Ferreira Paulo Cavalcanti Gomes
Instituto de Bioquímica Médica, CCS, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Cell Cycle. 2006 Sep;5(17):1957-65. doi: 10.4161/cc.5.17.3125. Epub 2006 Sep 1.
Sister-chromatid separation and exit from mitosis require ubiquitin-mediated proteolysis of cell cycle regulators such as cyclin B and securin. The specificity of the reaction is controlled by an ubiquitin-ligase multiprotein complex known as APC (Anaphase Promoting Complex). Comparison of the coding sequences of Arabidopsis genes with the Genbank database reveals extensive homology of the predicted ORFs with the corresponding proteins of other eukaryotes, indicating that the APC is well conserved in plants. However, different from other eukaryotes, the Arabidopsis genes have some particular characteristics, such as the presence of two copies of the CDC27 gene. Furthermore, expression analyses of the AtAPC genes disclose complex profiles that differ, depending on the tissue examined. In actively dividing cell suspensions there is a direct correspondence between the rates of proliferation and mRNA levels from the AtAPC components. On the other hand, in plant organs, dark-grown seedlings and during leaf growth, this correlation is lost and the AtAPC genes are highly expressed in tissues with low overall cell division. Moreover, expression patterns diverge between the subunit genes, raising the possibility that there could be more than one form of the APC, which would execute distinct functions during plant development. The results suggest that an important layer of regulation of APC/C in plants could operate through subunit availability in specific tissues and/or cellular compartments.
姐妹染色单体分离以及退出有丝分裂需要泛素介导的细胞周期调节因子（如细胞周期蛋白B和分离酶）的蛋白水解作用。该反应的特异性由一种称为后期促进复合物（APC）的泛素连接酶多蛋白复合体控制。将拟南芥基因的编码序列与Genbank数据库进行比较，发现预测的开放阅读框（ORF）与其他真核生物的相应蛋白质具有广泛的同源性，这表明APC在植物中高度保守。然而，与其他真核生物不同的是，拟南芥基因具有一些特殊特征，例如存在两个CDC27基因拷贝。此外，对AtAPC基因的表达分析揭示了复杂的表达谱，这些表达谱因所检测的组织而异。在活跃分裂的细胞悬浮液中，AtAPC组分的增殖速率与mRNA水平之间存在直接对应关系。另一方面，在植物器官、黑暗生长的幼苗以及叶片生长过程中，这种相关性消失，AtAPC基因在总体细胞分裂率低的组织中高度表达。此外，亚基基因之间的表达模式存在差异，这增加了可能存在不止一种形式的APC的可能性，而这些APC在植物发育过程中可能执行不同的功能。结果表明，植物中APC/C调节的一个重要层面可能通过特定组织和/或细胞区室中的亚基可用性来发挥作用。
