Zaret K S, DiPersio C M, Jackson D A, Montigny W J, Weinstat D L
Section of Biochemistry, Brown University, Providence, RI 02912.
Proc Natl Acad Sci U S A. 1988 Dec;85(23):9076-80. doi: 10.1073/pnas.85.23.9076.
We sought to develop a cell line in which liver-specific transcription could be induced at will, to facilitate the study of factors that cause hepatocyte-specific transcription of the serum albumin gene in mice. We therefore created the H2.35 cell line from mouse hepatocytes infected with a temperature-sensitive strain of simian virus 40. During routine propagation at the permissive temperature, H2.35 cells exhibit extremely low levels of albumin transcription and mRNA. Albumin mRNA increases at least 100-fold when H2.35 cells are cultured at the restrictive temperature and in serum-free medium on a collagen substratum; the two latter conditions maintain the differentiated state of primary hepatocyte cultures. Although a major cause of the mRNA increase is posttranscriptional, the transcription rates of albumin and other liver-specific genes increase significantly. Transient-transfection experiments demonstrated that an induction of transcription is caused by activation of an albumin upstream sequence that was previously shown to enhance liver-specific transcription in transgenic mice. Thus, hepatocyte differentiation appears to be maintained in part by extracellular signals that stimulate the activity of a tissue-specific enhancer element.
我们试图建立一种细胞系，在该细胞系中可以随意诱导肝脏特异性转录，以促进对导致小鼠血清白蛋白基因肝细胞特异性转录的因素的研究。因此，我们从感染了温度敏感型猿猴病毒40株的小鼠肝细胞中创建了H2.35细胞系。在允许温度下进行常规传代培养时，H2.35细胞的白蛋白转录和mRNA水平极低。当H2.35细胞在限制温度下并在胶原基质上的无血清培养基中培养时，白蛋白mRNA至少增加100倍；后两种条件维持了原代肝细胞培养物的分化状态。尽管mRNA增加的主要原因是转录后水平的，但白蛋白和其他肝脏特异性基因的转录速率也显著增加。瞬时转染实验表明，转录的诱导是由白蛋白上游序列的激活引起的，该序列先前已被证明可增强转基因小鼠中的肝脏特异性转录。因此，肝细胞分化似乎部分是由刺激组织特异性增强子元件活性的细胞外信号维持的。
