Identification of multiple transcription factors, HLF, FTF, and E4BP4, controlling hepatitis B virus enhancer II
Identification of multiple transcription factors, HLF, FTF, and E4BP4, controlling hepatitis B virus enhancer II
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DOI：
10.1128/jvi.74.3.1241-1251.2000
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发表时间：
2000-02-01
影响因子：
5.4
通讯作者：
Hayashi, N
中科院分区：
文献类型：
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作者：
Ishida, H;Ueda, K;Hayashi, N
B型肝炎病毒（HBV）增强子II（EnII）是一种嗜肝顺式元件，负责HBV肝细胞特异性基因表达。已经证明多种转录因子与该区域相互作用。在这项研究中，从HBV核苷酸（nt）1640至1663在EnII的区域被证明是必要的增强子的活性，是另一个目标序列的推定转录因子。为了阐明与该区域结合的因子，我们使用酵母单杂交筛选系统，从人成人肝脏cDNA文库中克隆了三个转录因子HLF、FTF和E4 BP 4。所有这些因子都对nt 1640 - 1663序列具有结合亲和力。研究这些因子对转录调控的影响发现，HLF和FTF在nt 1640至1663具有刺激活性，而E4 BP 4具有抑制作用。FTF协同激活3.5-kb RNA和2.4/2.1-kb RNA转录在瞬时转染试验与HBV表达载体。然而，ELF只激活3.5 kb的RNA转录，在引物延伸分析中，HLF强烈刺激前基因组RNA的合成相比，前核心RNA。因此，FTF刺激第二增强子的活性，而HLF刺激核心上游调控序列的活性，其仅影响核心启动子，并且对前基因组RNA合成具有主导作用。
Hepatitis B virus (HBV) enhancer II (EnII) is a hepatotropic cis element which is responsible for the hepatocyte-specific gene expression of HBV. Multiple transcription factors have been demonstrated to interact with this region. In this study, the region from HBV nucleotides (nt) 1640 to 1663 in EnII was demonstrated to be essential for enhancer activity and to be another target sequence of putative transcription factors. To elucidate the factors which bind to this region, we used a yeast one-hybrid screening system and cloned three transcription factors, HLF, FTF, and E4BP4, from a human adult liver cDNA library. All of these factors had binding affinity to the sequence from nt 1640 to 1663. Investigation of the effects of these factors on transcriptional regulation revealed that HLF and FTF had stimulatory activity on nt 1640 to 1663, whereas E4BP4 had a suppressing effect. FTF coordinately activated both 3.5-kb RNA and 2.4/2.1-kb RNA transcription in a transient transfection assay with an HBV expression vector. ELF, however, activated only 3.5-kb RNA transcription, and in primer extension analysis, HLF strongly stimulated the synthesis of pregenome RNA compared to precore RNA. Thus, FTF stimulated the activity of the second enhancer, while HLF stimulated the activity of the core upstream regulatory sequence, which affects only the core promoter, and had a dominant effect on the pregenome RNA synthesis.