Souleimani A, Asselin C
Département d'anatomie et de biologie cellulaire, Faculté de Médecine, Université de Sherbrooke, Québec, Canada.
FEBS Lett. 1993 Jul 12;326(1-3):45-50. doi: 10.1016/0014-5793(93)81758-r.
The human colon carcinoma cell line Caco-2 spontaneously undergoes enterocytic differentiation in culture. We used sodium butyrate to modify differentiation and growth properties of this cell line and considered c-myc expression as a potential target. Degradation of normal c-myc mRNAs with a half-life of 20 min is not coupled to translation in this cell line, as determined by cycloheximide treatment. We show that butyrate reduces c-myc mRNA levels after a 30 min delay. Butyrate does not affect c-myc expression at the level of transcriptional initiation or elongation, as determined by run-on analysis, but at a post-transcriptional level. Cycloheximide blocks butyrate-dependent reduction of c-myc mRNA levels. Cross-linking experiments show that a 34 kDa protein binds specifically to the c-myc AU-rich instability determinant found in the 3'-untranslated region (ARE). Binding of this protein to the ARE is not modulated by butyrate or cycloheximide. These experiments suggest that butyrate induces a factor involved in c-myc mRNA degradation that differs from the known ARE-associated proteins. Post-transcriptional modification of gene expression could be one of the major targets for this anti-proliferative agent.
人结肠癌细胞系Caco-2在培养过程中会自发地进行肠上皮细胞分化。我们使用丁酸钠来改变该细胞系的分化和生长特性，并将c-myc表达视为一个潜在靶点。通过环己酰亚胺处理确定，在该细胞系中，半衰期为20分钟的正常c-myc mRNA的降解与翻译无关。我们发现，丁酸钠在延迟30分钟后会降低c-myc mRNA水平。通过连续分析确定，丁酸钠在转录起始或延伸水平上不影响c-myc表达，而是在转录后水平上起作用。环己酰亚胺可阻断丁酸钠依赖的c-myc mRNA水平降低。交联实验表明，一种34 kDa的蛋白质特异性结合于3'非翻译区（ARE）中发现的富含AU的c-myc不稳定决定簇。该蛋白质与ARE的结合不受丁酸钠或环己酰亚胺的调节。这些实验表明，丁酸钠诱导了一种参与c-myc mRNA降解的因子，该因子不同于已知的与ARE相关的蛋白质。基因表达的转录后修饰可能是这种抗增殖剂的主要靶点之一。
