The 58-kDa microspherule protein (MSP58), a nucleolar protein, interacts with nucleolar protein p120
The 58-kDa microspherule protein (MSP58), a nucleolar protein, interacts with nucleolar protein p120
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DOI：
10.1046/j.1432-1327.1998.2530734.x
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发表时间：
1998-05-01
期刊：
影响因子：
--
通讯作者：
Busch, H
中科院分区：
文献类型：
--
作者：
Ren, Y;Busch, RK;Busch, H
p120蛋白是一种与增殖相关的核仁蛋白，在细胞周期的G1期早期可检测到，在S期早期达到峰值。大多数人类恶性肿瘤含有比正常静止细胞高得多的p120蛋白。为了鉴定p120相关蛋白，以p120蛋白为诱饵进行酵母双杂交筛选。两个阳性克隆编码了一种新蛋白的部分，命名为微球蛋白58 kDa （MSP58）。msp58mrna的长度为1.9 kb，通过HeLa核仁蛋白的Western blotting显示，msp58mrna编码约58-kDa的462个氨基酸的多肽。小鼠MSP58同源物与人类MSP58同源物的氨基酸相似性为97%，但在酵母基因组中未发现MSP58同源物。MSP58的n端区域含有富含丝氨酸的簇，其c端区域具有卷曲结构域。在昆虫Sf9细胞中，重组蛋白p120和MSP58相互关联，证实了酵母双杂交实验的结果。缺失突变表明，MSP58与p120的结合需要在p120的n端区域和MSP58蛋白的c端区域中存在一个以前未被识别的螺旋结构域。免疫荧光显示MSP58蛋白定位于核仁的微球中。当放线菌素d处理HeLa细胞时，抗MSP58 Ig标记核仁“帽”，当MSP58蛋白在COS-7细胞中过表达时，核仁不规则增大，提示MSP58可能影响核仁的大小和形状。
Protein p120 is a proliferation-related nucleolar protein which is detectable early in the G1 phase of the cell cycle and peaks early in the S phase. Most human malignant tumors contain much higher levels of protein p120 than normal resting cells. To identify p120-associated protein(s), a yeast two-hybrid screen was carried out using protein p120 as the bait. Two positive clones encoded portions of a novel protein, designated microspherule protein 58 kDa (MSP58). MSP58 mRNA is 1.9 kb and encodes an approximately 58-kDa polypeptide of 462 amino acids as shown by Western blotting of HeLa nucleolar proteins. The mouse MSP58 homolog has 97% amino acid similarity to human MSP58, but no MSP58 homolog was found in the yeast genome. The MSP58 N-terminal region contains serine-rich clusters and its C-terminal region has a coiled-toil domain. In insect Sf9 cells, recombinant p120 and MSP58 proteins associated with each other, confirming the results of the yeast two-hybrid assay. Deletion mutations revealed that the binding of MSP58 to p120 required a previously unrecognized coiled-coil domain within the N-terminal region of p120 and the C-terminal region of MSP58 protein. Immunofluorescence indicated that the MSP58 protein is localized in microspherules in the nucleolus. Anti-MSP58 Ig labeled nucleolar 'caps' when HeLa cells were treated with actinomycin D. When the MSP58 protein was overexpressed in COS-7 cells, the nucleolus became irregularly enlarged, which suggests that MSP58 may affect the size and shape of the nucleolus.