Kähäri V M, Olsen D R, Rhudy R W, Carrillo P, Chen Y Q, Uitto J
Department of Dermatology, Jefferson Medical Colleg, Thomas Jefferson University, Philadelphia, Pennsylvania.
Lab Invest. 1992 May;66(5):580-8.
Transforming growth factor-beta s (TGF-beta) are potent enhancers of the expression of several connective tissue genes. In this study we examined the effects of TGF-beta 1 and TGF-beta 2 on human elastin mRNA abundance, promoter activity, and mRNA stability in cultured human skin fibroblasts. Treatment of cell cultures with varying concentrations of TGF-beta 1 or TGF-beta 2 for 24 hours resulted in a dose-dependent increase in the elastin mRNA steady-state levels, with a maximum enhancement of approximately 30-fold being noted with 1 ng/ml. Addition of cycloheximide (10 micrograms/ml) failed to block up-regulation of elastin gene expression by TGF-beta, indicating that this effect can occur in the absence of active protein synthesis. Furthermore, TGF-beta elicited enhancement of elastin mRNA levels could be abrogated by tumor necrosis factor-alpha and partially counteracted by interferon-gamma. Transient transfections of human skin fibroblasts with elastin promoter/chloramphenicol acetyl-transferase reporter gene constructs, which contained up to approximately 5 kb of the 5' flanking DNA, revealed no change in the promoter activity in the presence of TGF-beta. However, TGF-beta appeared to stabilize the elastin mRNA transcripts as determined by Northern hybridizations after inhibition of initiation of the transcription. As a result of this stabilization, the elastin mRNA levels were clearly detectable in TGF-beta 1-treated cultures even up to 48 hours after inhibition of transcription while they were undetectable in the control cells after 24 hours of incubation. These results demonstrate that TGF-beta 1 and TGF-beta 2 are potent enhancers of elastin gene expression and that this effect is mediated, at least in part, post-transcriptionally. These results suggest that TGF-beta s are involved in regulation of elastin deposition during fetal development and tissue repair, as well as in pathological conditions.
转化生长因子-β（TGF-β）是几种结缔组织基因表达的强效增强剂。在本研究中，我们检测了TGF-β1和TGF-β2对培养的人皮肤成纤维细胞中人弹性蛋白mRNA丰度、启动子活性和mRNA稳定性的影响。用不同浓度的TGF-β1或TGF-β2处理细胞培养物24小时，导致弹性蛋白mRNA稳态水平呈剂量依赖性增加，在1 ng/ml时最大增强约30倍。添加环己酰亚胺（10微克/毫升）未能阻断TGF-β对弹性蛋白基因表达的上调作用，表明这种效应可以在无活性蛋白质合成的情况下发生。此外，TGF-β引起的弹性蛋白mRNA水平增强可被肿瘤坏死因子-α消除，并被干扰素-γ部分抵消。用人弹性蛋白启动子/氯霉素乙酰转移酶报告基因构建体瞬时转染人皮肤成纤维细胞，该构建体包含高达约5 kb的5'侧翼DNA，结果显示在TGF-β存在下启动子活性无变化。然而，如转录起始抑制后的Northern杂交所确定，TGF-β似乎稳定了弹性蛋白mRNA转录本。由于这种稳定性，在转录抑制后长达48小时，在TGF-β1处理的培养物中仍可清楚检测到弹性蛋白mRNA水平，而在对照细胞孵育24小时后则检测不到。这些结果表明，TGF-β1和TGF-β2是弹性蛋白基因表达的强效增强剂，且这种效应至少部分是在转录后介导的。这些结果提示，TGF-β参与胎儿发育和组织修复过程中弹性蛋白沉积的调节，以及病理状态下的调节。
