Minta J O, Fung M, Paramaswara B
Department of Laboratory Medicine and Pathobiology, Medical Sciences Building, University of Toronto, Toronto, ON M5S 1A8, Canada.
Biochim Biophys Acta. 1998 Nov 8;1442(2-3):286-95. doi: 10.1016/s0167-4781(98)00189-4.
We have investigated the effects of IL-1 and IL-6 on human complement factor I (CFI) production by Hep G2 cells. IL-6 treatment caused a dose- and time-dependent increase in CFI secretion while IL-1 did not demonstrate such effects. The increase in CFI synthesis correlated with increase in CFI mRNA levels. The half-life of CFI mRNA in untreated cells was approx. 23 h and this was increased to 31 h (26% increase) following induction with IL-6. The IL-6 induced increase in CFI gene expression was inhibited by actinomycin D indicating regulatory effects at the level of transcription. Nuclear run-on experiments showed that IL-6 increased the rate of CFI gene transcription 4.2-fold. Transient transfection analysis of chloramphenicol acetyltransferase reporter gene constructs containing truncated segments of the 5'-flanking region of CFI gene showed that the cis-acting sequence(s) controlling the IL-6 inducible transcription resides in an 83 bp region located between -738 bp and -655 bp relative to the transcription start site. Our results indicate that the upregulation of CFI gene expression by IL-6 involves a coordinate effort at the level of transcription and mRNA stability, with the enhanced rate of transcription being the principal mechanism.
我们研究了白细胞介素-1（IL-1）和白细胞介素-6（IL-6）对Hep G2细胞产生人补体因子I（CFI）的影响。IL-6处理导致CFI分泌呈剂量和时间依赖性增加，而IL-1未显示出此类作用。CFI合成的增加与CFI mRNA水平的增加相关。未处理细胞中CFI mRNA的半衰期约为23小时，在用IL-6诱导后增加到31小时（增加26%）。放线菌素D抑制了IL-6诱导的CFI基因表达增加，表明在转录水平存在调节作用。核转录实验表明，IL-6使CFI基因转录速率提高了4.2倍。对含有CFI基因5'侧翼区截短片段的氯霉素乙酰转移酶报告基因构建体进行瞬时转染分析表明，控制IL-6诱导转录的顺式作用序列位于相对于转录起始位点-738 bp至-655 bp之间的83 bp区域。我们的结果表明，IL-6对CFI基因表达的上调涉及转录和mRNA稳定性水平的协同作用，转录速率的提高是主要机制。
