Kandasamy Muthugapatti K, McKinney Elizabeth C, Meagher Richard B
Department of Genetics, Life Sciences Building, University of Georgia, Athens, GA 30602, USA.
Plant J. 2003 Mar;33(5):939-48. doi: 10.1046/j.1365-313x.2003.01691.x.
Arabidopsis encodes at least eight actin-related proteins (ARPs) most of which have orthologs in other distant organisms. To gain insight into the role of ARPs in plants, we have examined the spatial expression and subcellular distribution of two highly divergent Arabidopsis ARPs, AtARP4 and AtARP7. AtARP4 is a homolog of human BAF53 and yeast Arp4, and AtARP7 is a novel, ancient and plant-specific actin-related protein that is not distinctly related to any known ARPs from other kingdoms. Analysis of both these proteins with AtARP4- and AtARP7-specific antibodies revealed that they were most abundant in young meristematic and floral tissues, but were expressed constitutively in all organs and cell types irrespective of their developmental stage. Immunofluorescence studies showed that both AtARP4 and AtARP7 were localized predominantly to the nucleus during interphase. In mitotic cells lacking a nuclear envelope (e.g. metaphase, anaphase, and early telophase stages), these ARPs were excluded from the condensed chromosomes and dispersed throughout the cytoplasm. In contrast, a putative Arabidopsis histone H2B protein remained associated with the interphase nuclei as well as chromosomes throughout the cell cycle. Based on our results and data on the yeast ortholog of AtARP4, these two nuclear plant ARPs may be involved in the modulation of chromatin structure and transcriptional regulation mainly in interphase cells.
拟南芥编码至少八种肌动蛋白相关蛋白（ARPs），其中大多数在其他远缘生物中具有直系同源物。为了深入了解ARPs在植物中的作用，我们研究了两种高度不同的拟南芥ARPs，AtARP4和AtARP7的空间表达和亚细胞分布。AtARP4是人类BAF53和酵母Arp4的同源物，AtARP7是一种新颖的、古老的且植物特有的肌动蛋白相关蛋白，与其他界的任何已知ARPs没有明显关系。用AtARP4和AtARP7特异性抗体对这两种蛋白进行分析表明，它们在幼嫩的分生组织和花组织中最为丰富，但在所有器官和细胞类型中均持续表达，与它们的发育阶段无关。免疫荧光研究表明，在间期，AtARP4和AtARP7主要定位于细胞核。在缺乏核膜的有丝分裂细胞中（例如中期、后期和早期末期阶段），这些ARPs被排除在浓缩染色体之外并分散在整个细胞质中。相反，一种推定的拟南芥组蛋白H2B蛋白在整个细胞周期中都与间期核以及染色体相关联。根据我们的结果以及关于AtARP4酵母直系同源物的数据，这两种核植物ARPs可能主要在间期细胞中参与染色质结构的调节和转录调控。
