Role of pRb in Osteogenesis, Cell Cycle Exit and Cancer

pRb 在成骨、细胞周期退出和癌症中的作用

• 批准号: 6711779
• 负责人: Philip W. Hinds
• 金额: $ 39.85万
• 依托单位: TUFTS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6711779
• 关键词: DNA replication; apoptosis; biomarker; bone development; cell cycle; cell cycle proteins; cell growth regulation; cell proliferation; cell senescence; gene expression; genetic regulation; genetic transcription; genetically modified animals; immunoprecipitation; laboratory mouse; microarray technology; molecular cloning; osteogenesis; osteosarcoma; retinoblastoma protein; transcription factor; tumor suppressor proteins

DESCRIPTION (provided by applicant): The retinoblastoma protein, pRb, controls entry into the S phase of the cell cycle and acts as a tumor suppressor in many tissues. Re-introduction of pRb into tumor cells results in growth arrest due in part to E2F-dependent transcriptional repression of S phase genes. pRb may also be involved in terminal cell cycle exit as an instigator of E2F-independent senescence or differentiation programs. The irreversibility of pRb-induced cell cycle exit is illustrated by our observation that when shifted to the nonpermissive temperature, SAOS-2 cells previously arrested by temperature-sensitive pRb (tspRb) enter S phase but do not proliferate, and instead die as a result of apoptosis. These results suggest that in addition to repressing E2F-dependent transcription and S phase entry pRb initiates an irreversible growth suppressive program. To better understand these growth inhibitory properties of pRb, we have studied the role of pRb in senescence and differentiation. First, we have found that pRb induces p27kipi post-transcriptionally independent of E2F regulation. This induction is required for pRb-mediated Gi arrest and senescence. While the mechanism of this induction is unclear, our evidence indicates that it is related to cytoskeletal changes that result from alterations in transcriptional patterns soon after pRb expression. We have uncovered a second important function of pRb in cell cycle exit that is the result of pRb's ability to interact with the transcription factor CBFA1. This factor is required for bone development and expression of late markers of osteogenesis. We find that pRb can act as a direct coactivator of CBFA1 by binding to this protein at promoter sites within certain CBFA 1-regulated genes. The physiological relevance of this interaction is illustrated by the observation that cells lacking pRb fail to achieve complete osteogenic differentiation, nor do they undergo CBFA1 dependent growth arrest, even though CBFA1 protein levels are induced normally. These multiple growth suppressive properties of pRb may explain the prevalence of pRb mutations in osteosarcoma. Our current goal is to elucidate the mechanisms of CBFA1 transcriptional activation and senescence induction by pRb and to identify genes regulated by pRb in these processes. To address these issues we will: 1) Explore the mechanism through which pRb activates CBFA 1-dependent transcription. 2) Investigate the pRb-dependent proliferation arrest in senescent cells and in cells expressing CBFA1. 3) Determine the consequences of pRb loss on osteoblast and osteocyte phenotypes in vitro and in vivo. 4) Identify novel changes in transcription patterns in cells expressing temperature-sensitive pRb.

描述（由申请方提供）：视网膜母细胞瘤蛋白，pRb，对照品 进入细胞周期的S期，并在许多肿瘤中作为肿瘤抑制因子。 组织中pRb重新导入肿瘤细胞导致生长停滞， 部分与S期基因的E2 F依赖性转录抑制有关。pRb可以 也参与终末细胞周期退出作为一个煽动者 不依赖E2 F的衰老或分化程序。的不可逆性 pRb诱导的细胞周期退出通过我们的观察说明， 在非允许温度下，SAOS-2细胞先前被 温度敏感pRb（tspRb）进入S期但不增殖， 而是由于细胞凋亡而死亡。这些结果表明，除了 抑制E2 F依赖的转录和S期进入pRb启动了一个新的细胞周期， 不可逆转的生长抑制计划。为了更好地理解这些增长 pRb的抑制特性，我们已经研究了pRb在衰老中的作用， 分化首先，我们发现pRb诱导p27 kipi 转录后独立于E2 F调节。这个归纳是 pRb介导的Gi停滞和衰老所需的。虽然这种机制 诱导尚不清楚，我们的证据表明它与细胞骨架有关 pRb后不久转录模式改变引起的变化 表情我们揭示了pRb在细胞周期中的第二个重要功能 出口，这是pRb与转录相互作用的能力的结果 CBFA 1因子。该因子是骨发育和表达 成骨的晚期标志物。我们发现pRb可以作为一种直接的共激活剂 通过在某些CBFA内的启动子位点与该蛋白结合， 1-调控基因这种相互作用的生理相关性是 通过观察到缺乏pRb的细胞不能实现完全的细胞分化来说明。 成骨分化，也不经历CBFA 1依赖性生长停滞， 尽管CBFA 1蛋白水平被正常诱导。这些多重增长 pRb的抑制特性可以解释pRb突变的流行， 骨肉瘤我们目前的目标是阐明CBFA 1的机制， 转录激活和衰老诱导，并确定 在这些过程中由pRb调控的基因。为了解决这些问题，我们将：1） 探讨pRb激活CBFA 1依赖性的机制 转录。2)研究pRb依赖性增殖阻滞在 衰老细胞和表达CBFA 1的细胞中。3)确定...的后果 体外和体内成骨细胞和骨细胞表型的pRb缺失。四、 鉴定表达以下蛋白的细胞中转录模式的新变化： 温度敏感pRb。