Wei Qiou, Eviatar-Ribak Tamar, Miskimins W Keith, Miskimins Robin
Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota 57069, USA.
J Neurochem. 2007 Jun;101(5):1214-23. doi: 10.1111/j.1471-4159.2007.04488.x. Epub 2007 Apr 2.
Our previous studies have found that expression of p27 in oligodendrocytes enhances myelin basic protein (MBP) gene expression through a mechanism that involves the transcription factor Sp1. In this study we show that this activation only requires the N-terminal 45 amino acids of p27 containing a functional cyclin-binding motif. In an effort to identify other cofactors that are involved in the p27-mediated activation of MBP gene expression, a yeast two-hybrid assay was performed using an N-terminal truncated p27 and a mouse embryo cDNA library. Galectin-4 was found to interact with p27 in the yeast two-hybrid assay. This novel interaction was also confirmed using a glutathione-S-transferase interaction assay and immunoprecipitation assays. Expression of galectin-4 in primary oligodendrocytes was confirmed by western blot. Additionally, the MBP promoter could be activated by expression of galectin-4 in CG4 oligodendrocytes, similar to the effects of increased p27 levels. We also show that Sp1 and galectin-4 interact in cells, while a complex of all three proteins could not be found. We conclude that galectin-4 is involved in the p27-mediated activation of the MBP gene, possibly through modulation of the glycosylation status of the transcription factor Sp1.
我们之前的研究发现，少突胶质细胞中p27的表达通过一种涉及转录因子Sp1的机制增强髓鞘碱性蛋白（MBP）基因的表达。在本研究中，我们表明这种激活仅需要包含功能性细胞周期蛋白结合基序的p27的N端45个氨基酸。为了鉴定参与p27介导的MBP基因表达激活的其他辅助因子，使用N端截短的p27和小鼠胚胎cDNA文库进行了酵母双杂交试验。在酵母双杂交试验中发现半乳糖凝集素-4与p27相互作用。这种新的相互作用也通过谷胱甘肽-S-转移酶相互作用试验和免疫沉淀试验得到证实。通过蛋白质免疫印迹法证实了原代少突胶质细胞中半乳糖凝集素-4的表达。此外，在CG4少突胶质细胞中，半乳糖凝集素-4的表达可激活MBP启动子，类似于p27水平升高的作用。我们还表明，Sp1和半乳糖凝集素-4在细胞中相互作用，但未发现这三种蛋白质形成的复合物。我们得出结论，半乳糖凝集素-4可能通过调节转录因子Sp1的糖基化状态参与p27介导的MBP基因激活。
