Begbie M, Mueller C, Lillicrap D
Department of Pathology, Queen's University, Kingston, Ontario, Canada.
DNA Cell Biol. 1999 Feb;18(2):165-73. doi: 10.1089/104454999315556.
The regulatory regions of the genes for coagulation Factors VIII and IX contain binding sites for both liver-enriched and ubiquitous transcriptional regulators. We investigated the role of the liver-enriched protein, hepatic leukemia factor (HLF), in mediating transcriptional regulation of the Factor VIII and IX genes. Using transient transfection assays in HepG2 hepatoma cells, we demonstrated the ability of HLF alone and in synergistic combination with the D-box binding protein (DBP), another proline and acidic-rich (PAR) protein family member, to transactivate these promoters. HLF is capable of binding to multiple sites in both the Factor VIII and Factor IX promoters. At least some of the synergistic activation of the Factor VIII promoter seen with HLF and DBP cotransfection can be attributed to increased binding of HLF-DBP heterodimers to two Factor VIII promoter sites. We have also demonstrated that an E2A-HLF chimera, derived from a t(17;19) translocation in pre-B acute lymphoblastic leukemia (ALL) cells, is capable of mediating expression from the Factor VIII and Factor IX promoters in both hepatoma cells and pre-B ALL cells. These observations indicate that the PAR family of transcription factors plays an important and complex role in regulating expression of the Factor VIII and Factor IX genes, involving the binding of both homodimeric and heterodimeric complexes of HLF and DBP to several sites in the promoters. Finally, these studies reaffirm the potential role of dimeric transcription factor complexes in mediating interactions with specific promoter elements, which, in the case of the Factor VIII promoter, results in dramatically enhanced binding of HLF-DBP heterodimers to two cis-acting sequences. These observations further our understanding of the role played by members of the PAR family of transcription factors in regulating expression of the Factor VIII and Factor IX genes.
凝血因子VIII和IX基因的调控区域含有肝脏富集型和普遍存在的转录调节因子的结合位点。我们研究了肝脏富集蛋白——肝脏白血病因子（HLF）在介导因子VIII和IX基因转录调控中的作用。通过在HepG2肝癌细胞中进行瞬时转染实验，我们证明了HLF单独以及与D框结合蛋白（DBP，另一种富含脯氨酸和酸性氨基酸的（PAR）蛋白家族成员）协同组合时，能够激活这些启动子。HLF能够结合因子VIII和因子IX启动子中的多个位点。HLF和DBP共转染时因子VIII启动子的至少部分协同激活可归因于HLF-DBP异二聚体与因子VIII启动子两个位点的结合增加。我们还证明，源自前B急性淋巴细胞白血病（ALL）细胞中t(17;19)易位的E2A-HLF嵌合体能够在肝癌细胞和前B ALL细胞中介导因子VIII和因子IX启动子的表达。这些观察结果表明，PAR转录因子家族在调节因子VIII和IX基因的表达中起着重要而复杂的作用，涉及HLF和DBP的同二聚体和异二聚体复合物与启动子中多个位点的结合。最后，这些研究再次证实了二聚体转录因子复合物在介导与特定启动子元件相互作用中的潜在作用，就因子VIII启动子而言，这导致HLF-DBP异二聚体与两个顺式作用序列的结合显著增强。这些观察结果进一步加深了我们对PAR转录因子家族成员在调节因子VIII和IX基因表达中所起作用的理解。
