Mad1 function is regulated through elements within the carboxy terminus
Mad1 function is regulated through elements within the carboxy terminus
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DOI：
10.1128/mcb.20.12.4253-4264.2000
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发表时间：
2000-06-01
影响因子：
5.3
通讯作者：
Segal, S
中科院分区：
文献类型：
--
作者：
Barrera-Hernandez, G;Cultraro, CM;Segal, S
MYC和Mad是碱性螺旋-环-螺旋亮氨酸拉链(bHLH-LZ)蛋白，它们与MAX异源二聚体结合DNA，从而影响Mac反应基因的转录。MYC-Max二聚体反式激活，而Mad-Max-mSin3复合体抑制Myc介导的转录激活。我们以前已经证明，在从增殖到分化的分子开关过程中，MAD1需要N端的mSin3结合域和位于中心的bHLH-LZ。在这里，我们证明了MAD1的羧基末端(CT)包含了先前未知的调控MAD1功能所需的基序。我们发现，去除Mad1的最后18个氨基酸(V区)会取消该蛋白的生长抑制功能和逆转Myc强加的分化阻断的能力。此外，V区的缺失会导致一种与DNA结合较弱的蛋白质，不再抑制Myc依赖的转录激活。相反，删除前面的24个氨基酸(区域IV)和区域V可以恢复DNA结合和转录抑制，这表明这两个区域之间存在功能相互作用。此外，IV区内的磷酸化似乎介导了这种相互作用。这些发现表明，在Mad1CT中存在新的调节元件。
Myc and Mad are basic helix-loop-helix leucine zipper (bHLH-LZ) proteins that heterodimerize with Max to bind DNA and thereby influence the transcription of Mac-responsive genes. Myc-Max dimers transactivate whereas Mad-Max-mSin3 complexes repress Myc-mediated transcriptional activation. We have previously shown that the N-terminal mSin3 binding domain and the centrally located bHLH-LZ are required for Mad1 to function during a molecular switch from proliferation to differentiation. Here we demonstrate that the carboxy terminus (CT) of Mad1 contains previously unidentified motifs necessary for the regulation of Mad1 function. We show that removal of the last 18 amino acids of Mad1 (region V) abolishes the growth-inhibitory function of the protein and the ability to reverse a Myc-imposed differentiation block Moreover, deletion of region V results in a protein that binds DNA weakly and no longer represses Myc-dependent transcriptional activation. In contrast, deletion of the preceding 24 amino acids (region IV) together with region V restores DNA binding and transcriptional repression, suggesting a functional interplay between these two regions. Furthermore, phosphorylation within region IV appears to mediate this interplay. These findings indicate that novel regulatory elements are present in the Mad1 CT.