Hepatocyte nuclear factor 3 beta contains two transcriptional activation domains, one of which is novel and conserved with the Drosophila fork head protein
Hepatocyte nuclear factor 3 beta contains two transcriptional activation domains, one of which is novel and conserved with the Drosophila fork head protein
复制标题
DOI：
10.1128/mcb.12.9.3723-3732.1992
复制
发表时间：
1992-09
影响因子：
5.3
通讯作者：
L. Pani;D. Overdier;A. Porcella;X. Qian;E. Lai;R. Costa
中科院分区：
文献类型：
--
作者：
L. Pani;D. Overdier;A. Porcella;X. Qian;E. Lai;R. Costa
肝细胞核因子3 （HNF-3）基因家族由三种蛋白（α、β和γ）组成，它们是参与多个肝脏基因协调表达的转录因子。这三种蛋白在其DNA结合域（I区）上具有很强的同源性，并且能够识别相同的DNA序列。它们在羧基端（II区和III区）也具有两个相似的氨基酸片段，在氨基端（IV区）具有第四段同源性。此外，HNF-3蛋白在I区、II区和III区与果蝇同源基因叉头同源，表明HNF-3可能是其哺乳动物同源物。为了确定参与转录激活的HNF-3 β蛋白结构域，我们使用了一个报告基因，其转录依赖于HNF-3的结合，用于肝癌细胞共转染试验，表达载体产生不同的截断的HNF-3 β蛋白。在HNF-3 β蛋白的羧基端（361 ~ 458个氨基酸）鉴定出一个不依赖于位置的活化结构域，包含保守区II和III。此外，改变II区和III区序列的位点定向突变证明了它们对反激活的重要性。II-III区域不具有与其他转录因子相同的氨基酸序列，可能定义一个新的激活基序。由保守区IV定义的HNF-3 β氨基末端序列也有助于反激活，但IV区活性需要II-III区结构域的参与。IV区富含丝氨酸氨基酸，并含有两个假定的酪蛋白激酶I磷酸化位点，这一特征与转录因子Pit-1/GHF-1和HNF-1描述的蛋白质基序相似。
The hepatocyte nuclear factor 3 (HNF-3) gene family is composed of three proteins (alpha, beta, and gamma) that are transcription factors involved in the coordinate expression of several liver genes. All three proteins share strong homology in their DNA binding domains (region I) and are able to recognize the same DNA sequence. They also possess two similar stretches of amino acids at the carboxyl terminus (regions II and III) and a fourth segment of homology at the amino terminus (region IV). Furthermore, the HNF-3 proteins demonstrate homology with the Drosophila homeotic gene fork head in regions I, II, and III, suggesting that HNF-3 may be its mammalian homolog. In order to define HNF-3 beta protein domains involved in transcriptional activation, we have used a reporter gene, whose transcription is dependent on HNF-3 binding, for hepatoma cell cotransfection assays with expression vectors that produced different truncated HNF-3 beta proteins. A position-independent activation domain which contained conserved regions II and III was identified at the carboxyl terminus of the HNF-3 beta protein (amino acids 361 to 458). Moreover, site-directed mutations that altered the sequences within regions II and III demonstrated their importance to transactivation. The region II-III domain does not possess amino acid sequences in common with other transcription factors and may define a novel activation motif. HNF-3 beta amino-terminal sequences defined by conserved region IV also contributed to transactivation, but region IV activity required the participation of the region II-III domain. Region IV is abundant in serine amino acids and contains two putative casein kinase I phosphorylation sites, a feature similar to protein motifs described for the transcription factors Pit-1/GHF-1 and HNF-1.