Brachyury-related transcription factor Tbx2 and repression of the melanocyte-specific TRP-1 promoter
Brachyury-related transcription factor Tbx2 and repression of the melanocyte-specific TRP-1 promoter
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DOI：
10.1128/mcb.18.9.5099
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发表时间：
1998-09-01
影响因子：
5.3
通讯作者：
Goding, CR
中科院分区：
文献类型：
--
作者：
Carreira, S;Dexter, TJ;Goding, CR
先前的工作已经证明，两个关键的黑素细胞特异性元件MSEu和MSEi在黑素细胞特异性酪氨酸酶相关蛋白1（TRP-1）启动子的表达中起关键作用。MSEu和MSEi，分别位于-237位和起始位点，结合一种称为MSF的黑素细胞特异性因子，但也被以前未表征的阻遏物识别，因为影响这些元件中任一个的突变导致黑色素瘤细胞中TRP-1启动子活性的强烈上调。在这里，我们表明，抑制介导的MSEu和MSEi也在黑素细胞中运作，我们还报告说，MSEu和MSEi的短尾相关的转录因子Tbx 2，最近描述的T-box家族的成员，和Tbx 2表达在黑素细胞和黑素母细胞细胞系，但不是在黑素母细胞前体细胞。虽然Tbx 2和MSF各自识别TRP-1 MSEu和MSEi基序，但与阻遏相关的是Tbx-2结合而不是MSF结合。几条证据倾向于指出短尾相关转录因子Tbx 2是TRP-1表达的阻遏物：MSEu和MSEi都结合Tbx 2，并且导致TRP-1启动子去阻遏的任一元件中的突变减少了Tbx 2的结合; TRP-1启动子，但不是酪氨酸酶、小眼症或甘油醛-3-磷酸脱氢酶（G3 PDH）启动子，在共转染测定中被Tbx 2抑制;高亲和力共有短尾畸形/Tbx 2结合位点能够组成型抑制异源IE110启动子的表达;并且低亲和性brachyury/Tbx 2结合位点能够介导G3 PDH启动子的Tbx 2依赖性阻遏，虽然我们不能排除存在另外的尚未鉴定的因子在体内TRP-1的负调节中起作用，这里提供的证据表明Tbx 2很可能是以前未鉴定的TRP阻遏物，1表达，因此可能代表了T-box家族成员转录抑制的第一个例子。
Previous work has demonstrated that two key melanocyte-specific elements termed the MSEu and MSEi play critical roles in the expression of the melanocyte-specific tyrosinase-related protein 1 (TRP-1) promoter. Both the MSEu and MSEi, located at position -237 and at the initiator, respectively, bind a melanocyte-specific factor termed MSF but are also recognized by a previously uncharacterized repressor, since mutations affecting either of these elements result in strong up-regulation of TRP-1 promoter activity in melanoma cells. Here we demonstrate that repression mediated by the MSEu and MSEi also operates in melanocytes, We also report that both the MSEu and MSEi are recognized by the brachyury-related transcription factor Tbx2, a member of the recently described T-box family, and that Tbx2 is expressed in melanocyte and melanoblast cell lines but not in melanoblast precursor cells. Although Tbx2 and MSF each recognize the TRP-1 MSEu and MSEi motifs, it is binding by Tbx-2 not binding by MSF, that correlates with repression. Several lines of evidence tend to point to the brachyury-related transcription factor Tbx2 as being the repressor of TRP-1 expression: both the MSEu and MSEi bind Tbx2, and mutations in either element that result in derepression of the TRP-1 promoter diminish binding by Tbx2; the TRP-1 promoter, but not the tyrosinase, microphthalmia, or glyceraldehyde-3-phosphate dehydrogenase (G3PDH) promoter, is repressed by Tbx2 in cotransfection assays; a high-affinity consensus brachyury/Tbx2-binding site is able to constitutively repress expression of the heterologous IE110 promoter; and a low-affinity brachyury/Tbx2 binding site is able to mediate Tbx2-dependent repression of the G3PDH promoter, Although we cannot rule out the presence of an additional, as yet unidentified factor playing a role in the negative regulation of TRP-1 in vivo, the evidence presented here suggests that Tbx2 most likely is the previously unidentified repressor of TRP-1 expression and as such is likely to represent the first example of transcriptional repression by a T-box family member.