The role of the plant-specific DNA-interacting 3xHMG-box proteins in mitosis (and meiosis)

细胞分裂的一个特征是基因组DNA显著浓缩成有丝分裂（或减数分裂）染色体。染色体的紧密化对于有丝分裂和减数分裂期间染色体的可靠分离，以及因此对于正确的遗传是至关重要的。在准备工作中，我们已经开始研究一个迄今为止尚未表征的植物特异性蛋白家族，包含三个HMG盒DNA结合结构域，称为3xHMG盒蛋白。两个拟南芥3xHMG盒蛋白与DNA相互作用，但与其他HMG盒蛋白不同，它们显示细胞周期依赖性表达，在经历有丝分裂（和减数分裂）的细胞中达到峰值。拟南芥3xHMG-box蛋白与浓缩的有丝分裂/减数分裂染色体相关，3xHMG-box 2通常与浓缩的染色体相关，而3xHMG-box 1显示出对45 S rDNA位点的明显偏好。目前，还不清楚这些蛋白质在有丝分裂/减数分裂中发挥的作用，因此我们打算在这个拟议的项目中解决这个问题。将分析两种3xHMG盒蛋白表达水平改变的植物可能的表型差异（相对于对照植物）、对染色体结构/分离、组蛋白修饰、45 S rDNA活性和细胞周期异常的影响。我们还分析了两种3xHMG盒蛋白之间的分子差异，并鉴定了与3xHMG盒蛋白相互作用的蛋白质，以了解更多关于它们的细胞功能。总之，该项目将深入了解3xHMG盒蛋白在细胞分裂中的生物学作用。

A characteristic of cell division is the remarkable condensation of the genomic DNA into mitotic (or meiotic) chromosomes. The compaction of the chromosomes is of fundamental importance for faithful chromosome segregation during mitosis and meiosis, and therefore for proper inheritance. In preparatory work, we have started studying a so far uncharacterised family of plant-specific proteins, containing three HMG-box DNAbinding domains, termed 3xHMG-box proteins. Two Arabidopsis 3xHMG-box proteins interact with DNA, but unlike other HMG-box proteins they display cell cycle dependent expression, peaking in cells undergoing mitosis (and meiosis). Both the Arabidopsis 3xHMG-box proteins associate with condensed mitotic/meiotic chromosomes and 3xHMG-box2 generally associates with condensed chromosomes, whereas 3xHMG-box1 displays a clear preference for 45S rDNA loci. Currently, it is unclear which role these proteins play during mitosis/meiosis, and therefore we intend to address this question in this proposed project. Plants with altered expression levels of the two 3xHMG-box proteins will be analysed for possible phenotypic differences (relative to control plants), for effects on chromosome structure/segregation, histone modifications, 45S rDNA activity and cell cycle abnormalities. We also analyse the molecular differences between the two 3xHMG-box proteins and identify proteins interacting with the 3xHMG-box proteins to learn more about their cellular function. In summary, this project will provide insight into the biological role of the 3xHMG-box proteins in cell division.