Gerits Nancy, Shiryaev Alexey, Kostenko Sergiy, Klenow Helle, Shiryaeva Olga, Johannessen Mona, Moens Ugo
Department of Microbiology and Virology, Faculty of Medicine, University of Tromsø, N-9037, Tromsø, Norway.
Cell Mol Biol Lett. 2009;14(4):548-74. doi: 10.2478/s11658-009-0020-6. Epub 2009 May 30.
The mitogen-activated protein kinase (MAPK) cascades regulate important cellular processes, including growth, differentiation, apoptosis, embryogenesis, motility and gene expression. Although MAPKs mostly appear to be constitutively expressed, the transcript levels of some MAPK-encoding genes increase upon treatment with specific stimuli. This applies to the MAPK-activated protein kinases MK2 and MK3. By contrast, the transcriptional regulation of the related MK5 has not yet been studied. The MK5 promoters of mouse, rat and human contain a plethora of putative transcription factor sites, and the spatio-temporal expression of MK5 suggests inducible transcription of the gene. We examined the transcription pattern of MK5 in different tissues, and studied the kinetics of MK5 expression at the transcriptional and/or translation level in PC12 cells exposed to arsenite, forskolin, KCl, lipopolysaccharide, spermine NONOate, retinoic acid, serum, phorbol ester, temperature shock, and vanadate. Cells exposed to forskolin display a transient increase in MK5 mRNA, despite their unaltered MK5 protein levels. The MK5 promoters of human, mouse and rat contain a cAMP-responsive element that binds the cAMP-responsive element-binding protein (CREB) in vitro. Luciferase reporter constructs containing an 850-base pair human MK5 promoter fragment encompassing the CRE showed a basal activity that was 10-fold higher than the corresponding construct in which the CRE motif was deleted. siRNA-mediated depletion of CREB had no effect on the endogenous MK5 protein levels. Several binding motifs for heat shock factor are dispersed in the mouse and rat promoter, and temperature shock transiently enhanced the MK5 transcript levels. None of the other tested stimuli had an effect on the MK5 mRNA or protein levels. Our results indicate an inducible regulation of MK5 transcription in response to specific stimuli. However, the MK5 protein levels remained unaffected by all the stimuli tested. There is still no explanation for the discrepancy between the increased mRNA and unchanged MK5 protein levels.
丝裂原活化蛋白激酶（MAPK）级联反应调节重要的细胞过程，包括生长、分化、凋亡、胚胎发生、运动和基因表达。尽管MAPK大多似乎是组成性表达的，但一些MAPK编码基因的转录水平在受到特定刺激后会增加。这适用于MAPK激活的蛋白激酶MK2和MK3。相比之下，相关的MK5的转录调控尚未得到研究。小鼠、大鼠和人类的MK5启动子包含大量假定的转录因子位点，并且MK5的时空表达表明该基因可诱导转录。我们检查了MK5在不同组织中的转录模式，并研究了暴露于亚砷酸盐、福斯高林、氯化钾、脂多糖、精胺NONOate、视黄酸、血清、佛波酯、温度休克和钒酸盐的PC12细胞中MK5在转录和/或翻译水平上的表达动力学。暴露于福斯高林的细胞显示MK5 mRNA有短暂增加，尽管其MK5蛋白水平未改变。人类、小鼠和大鼠的MK5启动子包含一个环磷酸腺苷反应元件（cAMP-responsive element），该元件在体外与环磷酸腺苷反应元件结合蛋白（CREB）结合。包含一个850个碱基对的人类MK5启动子片段（包含CRE）的荧光素酶报告构建体显示出比相应的缺失CRE基序的构建体高10倍的基础活性。RNA干扰介导的CREB缺失对内源性MK5蛋白水平没有影响。热休克因子的几个结合基序分散在小鼠和大鼠启动子中，温度休克短暂增强了MK5转录水平。其他测试刺激均未对MK5 mRNA或蛋白水平产生影响。我们的结果表明MK5转录可响应特定刺激进行诱导调节。然而，MK5蛋白水平不受所有测试刺激的影响。对于mRNA增加与MK5蛋白水平不变之间的差异仍没有解释。
