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

从21号染色体上的“唐氏综合征临界区”克隆的MNB/DYRK1A基因是与精神发育迟滞相关的有力候选基因。唐氏综合症。该基因编码一种双特异性蛋白激酶，其活性依赖于激活环中酪氨酸残基的光短化。在本研究中，我们检测了MNB/DYRK1A蛋白在HeLa细胞中的细胞内定位。MNB/DYRK1A的绿色荧光蛋白(GFP)融合蛋白在间期核内呈斑点状分布。有丝分裂中核膜破裂后，核膜呈弥漫状，定位于细胞质内，相对排斥浓缩的染色质区域。亚细胞分级研究表明，GFP-MNB/DYRK1A主要存在于核中的可溶组分中，而不是核基质中。GFP-MNB/DYRK1A突变体构建体(Y310F/Y312F)也表现出斑点状，表明核点的出现与这些酪氨酸残基的磷酸化无关。PML、SC-35、PCNA和SUMO-1以前也显示出类似的亚核点状分布模式；然而，共聚焦显微镜分析表明，它们都没有与GFP-MNB/DYRK1A共定位。除了有核点的细胞外，我们还观察到表达GFP-MNB/DYRK1A的细胞遍布细胞核。在这些细胞中观察到了多核现象，表明MNB/DYRK1A的过表达导致了HeLa细胞的多核。这些结果表明，在细胞周期中，MNB/DYRKlA在协调核分裂(有丝分裂)和胞质分裂(胞质分裂)中起着重要作用。对控制细胞分裂的微管蛋白和肌动蛋白等细胞囊蛋白进行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.