Breiling Achim, Sessa Luca, Orlando Valerio
Dulbecco Telethon Institute, Institute of Genetics and Biophysics, CNR, 80131 Naples, Italy.
Int Rev Cytol. 2007;258:83-136. doi: 10.1016/S0074-7696(07)58002-2.
Cellular phenotypes can be ascribed to different patterns of gene expression. Epigenetic mechanisms control the generation of different phenotypes from the same genotype. Thus differentiation is basically a process driven by changes in gene activity during development, often in response to transient factors or environmental stimuli. To keep the specific characteristics of cell types, tissue-specific gene expression patterns must be transmitted stably from one cell to the daughter cells, also in the absence of the early-acting determination factors. This heritability of patterns of active and inactive genes is enabled by epigenetic mechanisms that create a layer of information on top of the DNA sequence that ensures mitotic and sometimes also meiotic transmission of expression patterns. The proteins of the Polycomb and Trithorax group comprise such a cellular memory mechanism that preserves gene expression patterns through many rounds of cell division. This review provides an overview of the genetics and molecular biology of these maintenance proteins, concentrating mainly on mechanisms of Polycomb group-mediated repression.
细胞表型可归因于不同的基因表达模式。表观遗传机制控制着从相同基因型产生不同的表型。因此，分化基本上是一个在发育过程中由基因活性变化驱动的过程，通常是对瞬时因子或环境刺激的响应。为了保持细胞类型的特定特征，组织特异性基因表达模式必须从一个细胞稳定地传递给子细胞，即使在没有早期起作用的决定因子的情况下也是如此。活跃和不活跃基因模式的这种遗传性是由表观遗传机制实现的，这些机制在DNA序列之上创建了一层信息，确保有丝分裂以及有时减数分裂时表达模式的传递。多梳蛋白家族和三胸蛋白家族的蛋白质构成了这样一种细胞记忆机制，它通过多轮细胞分裂维持基因表达模式。本综述概述了这些维持蛋白的遗传学和分子生物学，主要集中在多梳蛋白家族介导的抑制机制上。
