Flowers C C, Flowers S P, Nabel G J
Howard Hughes Medical Institute, University of Michigan Medical Center, Department of Internal Medicine, Ann Arbor 48109-0650, USA.
Mol Med. 1998 Jun;4(6):402-12.
Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a 442 amino acid polypeptide-designated viral interferon regulatory factor (vIRF) that displays homology to members of the interferon regulatory factor (IRF) family that bind to consensus interferon sequences and transactivate cellular genes that can modulate growth inhibition. Studies were conducted to determine whether vIRF affects the growth suppression mediated by interferon-alpha (IFN-alpha) in a human B lymphocyte cell line.
The human B lymphocyte cell line Daudi, which is sensitive to the antiproliferative effects of IFN-alpha, was stably transfected to express vIRF, and the proliferative response of vIRF expressing cells to IFN-alpha was compared with controls. The effect of vIRF on IRF- 1 transactivation was analyzed by co-transfection of an IFN-alpha-responsive chloramphenicol acetyltransferase reporter and expression plasmids encoding IRF-1 and vIRF. Electrophoretic mobility shift assays were conducted to determine whether vIRF interferes with the DNA binding activity of IRF-1.
Daudi human B lymphocyte cells expressing vIRF were resistant to the antiproliferative effects of IFN-alpha, whereas wild-type Daudi or Daudi cells transformed with vector DNA were growth inhibited by IFN-alpha. The activation of an interferon-responsive reporter by IFN-alpha or IRF-1 was repressed by expression of vIRF. IRF-1 DNA binding activity was unaffected by vIRF, and vIRF alone did not bind to the interferon consensus sequence.
These studies revealed that vIRF functions to inhibit interferon-mediated growth control of a human B lymphocyte cell line by targeting IRF-1 transactivation of interferon-inducible genes. Since KSHV is a B lymphotropic herpesvirus associated with two forms of B lymphocyte neoplasms, these effects of vIRF likely contribute to B cell oncogenesis associated with KSHV infection.
卡波西肉瘤相关疱疹病毒（KSHV）编码一种442个氨基酸的多肽，称为病毒干扰素调节因子（vIRF），它与干扰素调节因子（IRF）家族成员具有同源性，这些成员可结合共有干扰素序列并激活可调节生长抑制的细胞基因。开展研究以确定vIRF是否影响人B淋巴细胞系中由α干扰素（IFN-α）介导的生长抑制。
对IFN-α的抗增殖作用敏感的人B淋巴细胞系Daudi被稳定转染以表达vIRF，并将表达vIRF的细胞对IFN-α的增殖反应与对照进行比较。通过共转染IFN-α反应性氯霉素乙酰转移酶报告基因以及编码IRF-1和vIRF的表达质粒，分析vIRF对IRF-1反式激活的影响。进行电泳迁移率变动分析以确定vIRF是否干扰IRF-1的DNA结合活性。
表达vIRF的Daudi人B淋巴细胞对IFN-α的抗增殖作用具有抗性，而野生型Daudi或用载体DNA转化的Daudi细胞则被IFN-α抑制生长。vIRF的表达抑制了IFN-α或IRF-1对干扰素反应性报告基因的激活。IRF-1的DNA结合活性不受vIRF影响，并且单独的vIRF不与干扰素共有序列结合。
这些研究表明，vIRF通过靶向干扰素诱导基因的IRF-1反式激活来抑制人B淋巴细胞系中干扰素介导的生长控制。由于KSHV是一种与两种形式的B淋巴细胞肿瘤相关的嗜B淋巴细胞疱疹病毒，vIRF的这些作用可能有助于与KSHV感染相关的B细胞肿瘤发生。
