PROHIBITION GENE IN GROWTH CONTROL AND TUMOR SUPPRESSION

该提案的主要重点是了解prohibitin的肿瘤抑制特性，prohibitin是一种位于人类染色体17 q21上靠近BRACA 1基因座的基因。 Prohibitin可诱导细胞G1/S期阻滞，在散发性乳腺癌的一个亚群中发现了Prohibitin突变。 没有资料是关于prohibitin诱导G1/S期阻滞的机制。 我们最近的研究表明，prohibitin可以与Rb家族蛋白，以及Raf- 1，一个重要的信号分子物理相互作用。 Prohibitin能够抑制多种细胞系中集落的形成;这种抑制可以被Raf-1逆转。 此外，抑制素可抑制Rb蛋白的主要下游靶标E2 F的转录活性。 抑制素介导的B细胞系中E2 F活性的抑制可以通过刺激IgM受体来逆转。本申请中提出的实验旨在理解抑制素诱导细胞生长停滞的分子机制。 将对prohibitin进行详细的突变分析，以鉴定参与影响生长抑制、对Raf-1蛋白的应答以及抑制E2 F活性的prohibitin区域。 将详细研究E2 F的E2 F的抑制机制，特别强调HDAC 1在这一过程中的作用。我们还将尝试了解上游信号，特别是Raf-1和MAP激酶通路是如何调节抑制素功能的。 在相同的背景下，将建立在IgM受体介导的信号的抑制素的作用。 最后，我们将评估prohibitin基因和蛋白在人类肿瘤和肿瘤衍生细胞系中的状态。 我们将集中在乳腺癌以及B细胞淋巴瘤中抑制素失活的作用，并将评估突变是否导致生长控制的丧失。 我们相信，本提案中描述的研究将揭示一个知之甚少的肿瘤抑制基因在肿瘤发生中的作用，并将确定设计抗癌药物的新靶点。

The major focus of this proposal is to understand the tumor suppressive properties of prohibitin, a gene located on human chromosome 17q21 close to the BRACA1 locus. Prohibitin can induce a G1/S arrest in cells, and prohibitin mutations have been found in a subset of sporadic breast cancers. No information is available on the mechanisms by which prohibitin induces a G1/S arrest. Our recent studies have shown that prohibitin can physically interact with the Rb family proteins, as well as Raf- 1, a vital signaling molecule. Prohibitin is capable of suppressing the formation of colonies in a variety of cell lines; this suppression can be reversed by Raf-1. Further, prohibitin can repress the transcriptional activity of E2F, a major down- stream target of the Rb protein. Prohibitin mediated repression of E2F activity in B-cell lines can be reversed by stimulating the IgM receptors. The experiments proposed in this application aim at understanding the molecular mechanisms by which prohibitin induces growth arrest in cells. A detailed mutational analysis of prohibitin will be conducted, to identify the region of prohibitin involved in effecting growth suppression, response to Raf-1 protein as well as inhibition of E2F activity. The mechanisms involved in prohibitin-mediated repression of E2F will be studied in detail, with special emphasis on the role of HDAC1 in this process. Attempts will also be made to understand how prohibitin function is regulated by upstream signals, especially Raf-1 and MAP kinase pathway. In the same context, the role of prohibitin in IgM receptor-mediated signaling will be established. Lastly, we will assess the status of prohibitin gene and protein in human tumors and tumor derived cell lines. We will focus on the role of prohibitin inactivation in breast carcinomas as well as B-cell lymphomas, and it will be assessed whether the mutation has contributed to a loss of growth control. We believe that the studies described in this proposal will throw light on the role of a poorly understood tumor suppressor gene in oncogenesis, and will identify novel targets for designing anti-cancer agents.