Bertomeu Thierry, Morse David
Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal 4101 Sherbrooke Est, Montréal, Québec, Canada H1X 2B2.
Protist. 2007 Oct;158(4):473-85. doi: 10.1016/j.protis.2007.04.003. Epub 2007 Jun 18.
An AAA protein from the dinoflagellate Gonyaulax polyedra (GpAAA) with the unusual ability to rescue the phenotype of a yeast mutant lacking G1/S phase cyclins (cln1cln2cln3) has been isolated and the mechanism of rescue was characterized. We find that GpAAA is not a cyclin and has no similarity to any known cell cycle regulators. Instead, GpAAA forms a novel and strongly supported clade with bacterial spoIIIAA proteins and an Arabidopsis gene of unknown function. Since dinoflagellates cannot be transformed, we took advantage of the powerful genetic tools available for yeast. We find that rescue of the cln1cln2cln3 phenotype does not involve an effect on the CDK-inhibitor (CKI) Sic1p, as GpAAA does not alter the sensitivity to an inducible SIC1. Instead, Northern blot analyses show that GpAAA expression increases levels of CLB5, in agreement with the observation that GpAAA is unable to rescue the quadruple mutant cln1cln2cln3clb5. We propose that the increased transcription of CLB5 may be due to a protein remodeling function of GpAAA alleviating inhibition of the transcription factor SBF. Thus, although no known equivalents to the yeast SBF have been documented in dinoflagellates, we conclude that dinoflagellates could indeed utilize GpAAA as a cell cycle regulator.
已分离出一种来自多甲藻（Gonyaulax polyedra）的AAA蛋白（GpAAA），它具有挽救缺乏G1/S期细胞周期蛋白（cln1cln2cln3）的酵母突变体表型的非凡能力，并对其挽救机制进行了表征。我们发现GpAAA不是细胞周期蛋白，与任何已知的细胞周期调节因子都没有相似性。相反，GpAAA与细菌spoIIIAA蛋白和一个功能未知的拟南芥基因形成了一个新的、得到有力支持的进化枝。由于不能对甲藻进行转化，我们利用了酵母可用的强大遗传工具。我们发现挽救cln1cln2cln3表型并不涉及对CDK抑制剂（CKI）Sic1p的影响，因为GpAAA不会改变对可诱导SIC1的敏感性。相反，Northern印迹分析表明GpAAA的表达增加了CLB5的水平，这与GpAAA无法挽救四重突变体cln1cln2cln3clb5的观察结果一致。我们提出CLB5转录增加可能是由于GpAAA的蛋白质重塑功能减轻了对转录因子SBF的抑制。因此，尽管在甲藻中尚未记录到与酵母SBF等效的已知蛋白，但我们得出结论，甲藻确实可以利用GpAAA作为细胞周期调节因子。
