Deregulated E2F transcriptional activity in autonomously growing melanoma cells.
Deregulated E2F transcriptional activity in autonomously growing melanoma cells.
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DOI：
10.1084/jem.191.6.1005
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发表时间：
2000-03-20
期刊：
影响因子：
--
通讯作者：
Germino J
中科院分区：
文献类型：
--
作者：
Halaban R;Cheng E;Smicun Y;Germino J
视网膜母细胞瘤肿瘤抑制蛋白(PRB)的失活与黑色素瘤细胞有关，但这一表型的分子基础尚未阐明，另外的家族成员(p107和p130，统称为口袋蛋白)的状态或对下游靶标如E2F转录因子的影响尚不清楚。由于细胞周期进程依赖于E2F家族成员(E2F1-E2F6)的转录活性，其中大多数转录活性受Pocket蛋白抑制结合的调节，因此我们研究了正常和恶性黑素细胞中E2F-Pocket蛋白DNA结合活性。凝胶漂移分析表明，在有丝分裂原依赖的正常黑素细胞中，外部生长因子严格控制着促进生长的自由E2F DNA结合活性的水平，主要由E2F2和E2F4组成，以及抑制生长的E2F4-p130复合体。相反，在黑色素瘤细胞中，自由的E2F DNA结合活性(E2F2和E2F4，在较小程度上是E2F1，E2F3，偶尔还有E2F5)被结构性地维持在高水平，而不受外部黑素细胞有丝分裂原的影响。与正常黑素细胞相比，E2F1是唯一一个在黑色素瘤细胞中含量更丰富的家族成员，DNA结合活性大约增加了5倍，主要是由于二聚化伙伴DP1水平的类似增加。细胞周期蛋白D1、A2和E的持续高表达、持续的细胞周期蛋白依赖性激酶4(CDK4)和CDK2活性，以及过度磷酸化形式的pRB、p107和p130的存在，表明黑色素瘤细胞通过失活所有三种口袋蛋白和释放E2F活性而获得自主生长的能力，否则在正常黑素细胞中受到外部生长因子的严格调控。
Inactivation of the retinoblastoma tumor suppressor protein (pRb) has been implicated in melanoma cells, but the molecular basis for this phenotype has not yet been elucidated, and the status of additional family members (p107 and p130, together termed pocket proteins) or the consequences on downstream targets such as E2F transcription factors are not known. Because cell cycle progression is dependent on the transcriptional activity of E2F family members (E2F1–E2F6), most of them regulated by suppressive association with pocket proteins, we characterized E2F–pocket protein DNA binding activity in normal versus malignant human melanocytes. By gel shift analysis, we show that in mitogen-dependent normal melanocytes, external growth factors tightly controlled the levels of growth-promoting free E2F DNA binding activity, composed largely of E2F2 and E2F4, and the growth-suppressive E2F4–p130 complexes. In contrast, in melanoma cells, free E2F DNA binding activity (E2F2 and E2F4, to a lesser extent E2F1, E2F3, and occasionally E2F5), was constitutively maintained at high levels independently of external melanocyte mitogens. E2F1 was the only family member more abundant in the melanoma cells compared with normal melanocytes, and the approximately fivefold increase in DNA binding activity could be accounted for mostly by a similar increase in the levels of the dimerization partner DP1. The continuous high expression of cyclin D1, A2, and E, the persistent cyclin-dependent kinase 4 (CDK4) and CDK2 activities, and the presence of hyperphosphorylated forms of pRb, p107, and p130, suggest that melanoma cells acquired the capacity for autonomous growth through inactivation of all three pocket proteins and release of E2F activity, otherwise tightly regulated in normal melanocytes by external growth factors.
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影响因子：
8
作者：
Holmberg, C;Helin, K;Karlström, O
通讯作者：
Karlström, O
影响因子：
14.5
作者：
ADAMS, PD;KAELIN, WG
通讯作者：
KAELIN, WG
DOI：
10.1016/0165-1110(92)90018-5
发表时间：
1992-05-01
期刊：
MUTATION RESEARCH
影响因子：
--
作者：
GAUDRAY, P;SZEPETOWSKI, P;THEILLET, C
通讯作者：
THEILLET, C
DOI：
10.1073/pnas.93.26.15215
发表时间：
1996-12-24
影响因子：
11.1
作者：
GrayBablin, J;Zalvide, J;Keyomarsi, K
通讯作者：
Keyomarsi, K
影响因子：
8
作者：
Hiyama, H;Iavarone, A;Reeves, SA
通讯作者：
Reeves, SA