Regulation of replication and genome stability by B-Myb

所有细胞的特性都受基因模式的支配，这些基因模式被激活，以产生执行各种功能的蛋白质。特定的蛋白质(转录因子)起着分子开关的作用，控制那些应该被激活的基因。该项目旨在研究其中一种名为B-Myb的开关，它属于一小群控制细胞生长和分化的相关蛋白质。B-Myb是原始Myb蛋白，似乎对所有分裂细胞的基本过程都是必不可少的，而相关的c-Myb蛋白已经进化出更特殊的功能，最显著的是在调节血细胞发育方面。所有需要c-Myb的细胞也含有B-Myb，这引发了这样一个问题：这些蛋白质的共同来源是否反映在它们功能的重叠程度上。大量证据表明，B-Myb通过影响基因组的复制参与控制细胞分裂。有趣的是，最近的研究表明，B-Myb对复制的这种影响至少有一部分对于防止染色体损伤至关重要，例如，这种损伤可能导致癌症的发展。虽然细胞分裂是大多数细胞共有的基本过程，但一些细胞有一个适应其特定功能的改变的过程。一个例子是在早期胚胎中构成细胞内球的细胞类型。这些细胞被称为胚胎干细胞(ES细胞)，能够单独培养出成人的所有组织，并可以在实验室中几乎无限期地分离和生长，而不会以任何方式改变。ES细胞表达非常高水平的B-Myb，在缺乏B-Myb的情况下无法培养。该项目旨在准确定义B-Myb如何影响基因组的复制和稳定性，并确定它在也包含相关c-Myb蛋白的细胞中的作用是否不同。还将对正常细胞和ES细胞进行比较，以确定B-Myb是否在特殊的细胞分裂中发挥额外的作用。第二个主要目标是确定B-Myb发挥作用的分子机制，包括确定它控制的基因。该项目的主要方法将是降低细胞中B-Myb蛋白的水平，然后分析反映复制效率和基因组完整性的一系列参数。B-Myb水平的降低将通过化学方法(‘RNA干扰敲除’)实现，或者使用来自转基因小鼠的细胞，以便有可能在需要时移除B-Myb蛋白。这项研究将增加我们对细胞分裂和基因组稳定性控制的基础知识。这些发现可能对理解获得性染色体缺陷(如癌症)引起的疾病的潜在机制具有实际意义。了解B-Myb在ES细胞中的功能对于它们未来在转化医学中的应用将是至关重要的，特别是关于它在保持无限分裂能力而不损失基因组完整性方面的重要性。

The properties of all cells are governed by the patterns of genes that are turned on to give rise to the proteins that perform various functions. Specific proteins (transcription factors) act like molecular switches to control those genes that should be turned on. This project aims to investigate one of these switches called B-Myb, which belongs to a small group of related proteins that control cell growth and differentiation. B-Myb is the ancestral Myb protein and appears to be essential for fundamental processes in all dividing cells, whereas the related c-Myb protein has evolved more specialised functions, most notably in the regulation of blood cell development. All cells that require c-Myb also contain B-Myb, raising the issue of whether the common origin of these proteins is reflected in a degree of overlap in their function. A large body of evidence indicates that B-Myb is involved in the control of cell division through an influence on replication of the genome. Interestingly, recent studies have suggested that at least part of this influence of B-Myb on replication is crucial to prevent damage to chromosomes that could lead, for example, to the development of cancer. Although cellular division is a fundamental process shared by most cells, some cells have an altered process that is adapted to their particular function. An example is the cell type that constitutes the inner ball of cells in the early embryo. These cells, termed embryonic stem cells (ES cells), are individually capable of giving rise to all tissues of the adult and can be isolated and grown in the laboratory almost indefinitely without becoming changed in any way. ES cells express very high levels of B-Myb and cannot be cultured in its absence. This project aims to define precisely how B-Myb influences the replication and stability of the genome, and to determine whether its role is distinct in cells that also contain the related c-Myb protein. Comparison will also be made between normal cells and ES cells to determine if B-Myb performs additional roles in specialised cellular division. A secondary major aim is to identify the molecular mechanisms through which B-Myb acts, including identification of the genes that it controls. The main approach underlying the project will be to reduce the levels of B-Myb protein in cells and then to analyse a range of parameters that reflect the efficiency of replication and integrity of the genome. Reduction of B-Myb levels will be achieved chemically ('RNA interference knockdown') or using cells derived from mice that have been genetically modified so that it is possible to remove the B-Myb protein when desired. This study will increase our basic knowledge of the control of cellular division and genome stability. The findings may be of practical significance in terms of understanding mechanisms underlying diseases that result from acquired chromosomal defects (eg cancer). An understanding of the function of B-Myb in ES cells will be crucial in their future application in translational medicine, especially in relation to its importance in maintaining the capacity for indefinite division without loss of genomic integrity.