Involvement of TORC2, a CREB co-activator, in the in vivo-specific transcriptional control of HTLV-1.
Involvement of TORC2, a CREB co-activator, in the in vivo-specific transcriptional control of HTLV-1.
复制标题
DOI：
10.1186/1742-4690-6-73
复制
发表时间：
2009-08-11
期刊：
影响因子：
3.3
通讯作者：
Fujisawa J
中科院分区：
文献类型：
--
作者：
Jiang S;Inada T;Tanaka M;Furuta RA;Shingu K;Fujisawa J
人T细胞白血病病毒1型（HTLV-1）可引起成人T细胞白血病（ATL），但HTLV-1在感染者外周血中的表达受到强烈抑制。然而，这种抑制可能解释了ATL发展过程中的长潜伏期，它很容易逆转，并且通过体外培养感染的T细胞，病毒表达很快恢复。为了研究体内特异性转录抑制的机制，我们建立了小鼠模型，小鼠在HTLV-1增强子（EL4-Gax）的控制下，腹腔注射用表达GFP-Tax融合蛋白Gax的重组逆转录病毒转导的同源EL4 T -淋巴瘤细胞。Gax基因的转录在体内沉默，但在离体培养中迅速上调。整合Gax报告基因的分析表明，启动子DNA的CpG甲基化和组蛋白修饰都与可逆抑制无关。抑制LTR的chip分析显示，TFIIB和Pol-II的启动子结合减少，但CREB或CBP/p300与病毒增强子序列的结合没有变化。然而，在EL4-Gax细胞中，CREB的共同激活剂TORC2的表达在体内大幅下降，在离体培养中恢复到正常水平。TORC2的表达减少与细胞核向细胞质的易位有关。通过siRNA敲除实验证实，在EL4-Gax细胞中，TORC2是三个torc家族蛋白（TORC1, 2,3）的主要功能蛋白。这些结果表明，TORC2可能在HTLV-1的体内特异性转录控制中发挥重要作用。本研究为体内抑制HTLV-1表达的可逆机制提供了一种新的模型，该机制不存在大多数HTLV-1感染携带者和大量ATL病例的原代细胞中观察到的DNA甲基化或低乙酰化组蛋白。
Human T-cell leukemia virus type 1 (HTLV-1) causes adult T -cell leukemia (ATL) but the expression of HTLV-1 is strongly suppressed in the peripheral blood of infected people. However, such suppression, which may explain the long latency in the development of ATL, is readily reversible, and viral expression resumes quickly with ex vivo culture of infected T -cells. To investigate the mechanism of in vivo -specific transcriptional suppression, we established a mouse model in which mice were intraperitoneally administered syngeneic EL4 T -lymphoma cells transduced with a recombinant retrovirus expressing a GFP-Tax fusion protein, Gax, under the control of the HTLV-1 enhancer (EL4-Gax). Gax gene transcription was silenced in vivo but quickly up-regulated in ex vivo culture. Analysis of integrated Gax reporter gene demonstrated that neither CpG methylation of the promoter DNA nor histone modification was associated with the reversible suppression. ChIP-analysis of LTR under suppression revealed reduced promoter binding of TFIIB and Pol-II, but no change in the binding of CREB or CBP/p300 to the viral enhancer sequence. However, the expression of TORC2, a co-activator of CREB, decreased substantially in the EL4-Gax cells in vivo, and this returned to normal levels in ex vivo culture. The reduced expression of TORC2 was associated with translocation from the nucleus to the cytoplasm. A knock-down experiment with siRNA confirmed that TORC2 was the major functional protein of the three TORC-family proteins (TORC1, 2, 3) in EL4-Gax cells. These results suggest that the TORC2 may play an important role in the in vivo -specific transcriptional control of HTLV-1. This study provides a new model for the reversible mechanism that suppresses HTLV-1 expression in vivo without the DNA methylation or hypoacetylated histones that is observed in the primary cells of most HTLV-1 -infected carriers and a substantial number of ATL cases.
登录
查看更多内容
影响因子：
3.3
作者：
Boxus M;Twizere JC;Legros S;Dewulf JF;Kettmann R;Willems L
通讯作者：
Willems L
影响因子：
2.1
作者：
Bangham, CRM
通讯作者：
Bangham, CRM
影响因子：
5.4
作者：
FUJII, M;TSUCHIYA, H;SEIKI, M
通讯作者：
SEIKI, M
DOI：
10.1073/pnas.82.8.2277
发表时间：
1985-01-01
影响因子：
11.1
作者：
FUJISAWA, J;SEIKI, M;YOSHIDA, M
通讯作者：
YOSHIDA, M
影响因子：
4.8
作者：
Koga, H;Ohshima, T;Shimotohno, K
通讯作者：
Shimotohno, K