Epstein-Barr virus nuclear antigen 3C is a powerful repressor of transcription when tethered to DNA
Epstein-Barr virus nuclear antigen 3C is a powerful repressor of transcription when tethered to DNA
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DOI：
10.1128/jvi.70.4.2481-2489.1996
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发表时间：
1996-04-01
影响因子：
5.4
通讯作者：
Allday, MJ
中科院分区：
文献类型：
--
作者：
Bain, M;Watson, RJ;Allday, MJ
EB病毒（EBV）核抗原3C（EBNA 3C）的表达是EBV激活和永生化人B淋巴细胞所必需的。EBNA 3C由992个氨基酸组成，包括潜在的bZIP基序和富含酸性、脯氨酸和谷氨酰胺残基的区域。因此，EBNA 3C类似于几个基因表达的反式调节因子。最近已经表明，当EBNA 3C片段与GAL 4的DNA结合结构域融合时，可以激活报告基因表达（D.马歇尔和C.样品，J. Virol. 69：3624-3630，1995）。虽然EBNA 3C结合DNA，但尚未鉴定出EBNA 3C结合的特异性位点;为了测试全长EBNA 3C调节转录的能力，将EBNA 3C（氨基酸11至992）融合至GAL 4的DNA结合结构域。我们表明，这种融合蛋白不反式激活，而是一个有效的阻遏报告基因的表达。抑制依赖于GAL 4-EBNA 3C的剂量和报告质粒内GAL 4结合位点的存在。抑制不限于B细胞，也不具有物种或启动子特异性。阻遏作用与GAL 4结合位点相对于转录起始位点的位置无关。已经鉴定了EBNA 3C的片段（氨基酸280至525），其以与全长蛋白几乎相同的方式抑制表达;该片段富含酸性和脯氨酸残基。第二个较弱的阻遏物区域位于氨基酸280至525的C末端，该区域富含脯氨酸和谷氨酰胺残基。我们还显示EBNA 3C在体外与TFIID的TATA结合蛋白成分结合，这表明EBNA 3C可能与基础转录复合物通讯的机制。
The expression of Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is essential for the activation and immortalization of human B lymphocytes by EBV. EBNA3C consists of 992 amino acids and includes a potential bZIP motif and regions rich in acidic, proline, and glutamine residues. Thus, EBNA3C resembles several trans regulators of gene expression. It has recently been shown that a fragment of EBNA3C can activate reporter gene expression when fused to the DNA-binding domain of GAL4 (D. Marshall and C. Sample, J. Virol. 69:3624-3630, 1995). Although EBNA3C binds DNA, a specific site for EBNA3C binding has not been identified; to test the ability of full-length EBNA3C to regulate transcription, EBNA3C (amino acids 11 to 992) was fused to the DNA-binding domain of GAL4. We show that this fusion protein does not transactivate but rather is a potent repressor of reporter gene expression. Repression is dependent on the dose of GAL4-EBNA3C and on the presence of GAL4-binding sites within reporter plasmids. Repression is not restricted to B cells nor is it species or promoter specific. Repression is independent of the location of the GAL4-binding sites relative to the transcription start site. A fragment of EBNA3C (amino acids 280 to 525) which represses expression in a manner which is nearly identical to that of the full-length protein has been identified; this fragment is rich in acidic and proline residues. A second, less potent repressor region located C terminal to amino acids 280 to 525 has also been identified; this domain is rich in proline and glutamine residues. We also show binding of EBNA3C, in vitro, to the TATA-binding protein component of TFIID, and this suggests a mechanism by which EBNA3C may communicate with the basal transcription complex.