Function, of MNB/DYRK1A gene cloned from "Down syndrome critical region" on chromosome 21.

MNB/DYRK 1A基因克隆自21号染色体上的“唐氏综合征关键区”，是与先天愚型相关的精神发育迟滞的有力候选基因。唐氏综合症。该基因编码一种双特异性蛋白激酶，其活性取决于激活环中酪氨酸残基的磷酸化。在这项研究中，我们研究了MNB/DYRK 1A蛋白在HeLa细胞中的细胞内定位。MNB/DYRK 1A的绿色荧光蛋白（GFP）融合蛋白在间期核内呈斑点状。在有丝分裂中，核被膜破裂后，它呈弥漫性分布，位于细胞质中，与浓缩的染色质区域相对隔绝。亚细胞分级分离研究表明，GFP-MNB/DYRK 1A主要存在于从细胞核而不是在核基质中获得的可溶性级分中。GFP-MNB/DYRK 1A突变体（Y310 F/Y312 F）也显示出斑点状的图案，表明核点的出现与这些酪氨酸残基的磷酸化无关。先前已显示PML、SC-35、PCNA和SUMO-1的亚核分布的类似点状模式;然而，共聚焦显微镜分析显示它们均不与GFP-MNB/DYRK 1A共定位。除了具有核点的细胞之外，我们观察到在整个核中表达GFP-MNB/DYRK 1A的细胞。在这些细胞中，观察到多核，表明MNB/DYRK 1A的过表达导致HeLa细胞中的多核。这些结果表明，MNB/DYRKlA在细胞周期中协调核分裂（有丝分裂）与胞质分裂（胞质分裂）中起重要作用。对控制细胞分裂的微管蛋白和肌动蛋白等细胞内蛋白质的详细分析是很重要的。

MNB/DYRK1A gene cloned from "Down syndrome critical region" on chromosome 21 is a strong candidate for mental retardation associated with. Down syndrome. This gene encodes a dual-specificity protein kinase whose activity depends on the phoshorylation of tyrosine residues in the activation loop. In this study, we examined the intracellular localization of MNB/DYRK1A protein in HeLa cells. Green fluorescent protein (GFP) fusion protein of MNB/DYRK1A exhibited a speckled pattern inside the nucleus in interphase. After breakdown of the nuclear envelope in mitosis, it gave a diffuse pattern and located in the cytoplasm with relative exclusion from the condensed chromatin region. Subcellular fractionation study revealed that GFP-MNB/DYRK1A was predominantly found in the soluble fraction obtained from the nuclei rather than in the nuclear matrix. GFP-MNB/DYRK1A mutant construct (Y310F/Y312F) also showed the speckled pattern, indicating that the appearance of nuclear dot is independent of phosphorylation of these tyrosine residues. Similar punctate patterns of subnuclear distribution have previously been shown for PML, SC-35, PCNA, and SUMO-1; however, con focal microscopy analysis showed that none of them colocalized with GFP-MNB/DYRK1A. In addition to the cells with the nuclear dots, we observed cells expressing GFP-MNB/DYRK1A all over the nucleus. In these cells, the multinucleation was observed, indicating that the overexpression of MNB/DYRK1A leads to multinucleation in HeLa cells. These results suggest that MNB/DYRKlA play a significant role in coordinating nuclear division (mitosis) with cytoplasmic division (cytokinesis) during cell cycle. Detailed analysis of cytoskeltal proteins such as tubulin and actin, which control cell division, is important.