Perturbation analysis of heterochromatin-mediated gene silencing and somatic inheritance.
Perturbation analysis of heterochromatin-mediated gene silencing and somatic inheritance.
复制标题
DOI：
10.1371/journal.pgen.1001095
复制
发表时间：
2010-09-09
期刊：
影响因子：
4.5
通讯作者：
Ahmad K
中科院分区：
文献类型：
--
作者：
Schneiderman JI;Goldstein S;Ahmad K
真核基因组中的重复序列会诱导染色质介导的并置基因的基因沉默。许多促进或拮抗沉默的成分已被鉴定，但异染色质如何引起基因表达的多样化和可遗传的变化仍然是个谜。我们利用果蝇眼睛中的诱导性错误表达来恢复改变 bwD 等位基因引起的沉默的新因子，bwD 等位基因是重复卫星 DNA 的插入，可沉默同源染色体上的 bw+ 等位基因。诱导修饰剂允许在发育的不同时间扰动沉默，并区分影响沉默建立或维持的因素。我们发现多种染色质和 RNA 加工因子可以解除沉默的抑制。即使在分化的细胞中，大多数因子也有效，这意味着沉默的染色质仍然具有可塑性。然而，bantam microRNA或crooked-legs (crol)锌指蛋白的过度表达仅在循环细胞中表达时解除抑制沉默。 Crol 的过度表达会加速细胞周期，这是解除沉默抑制所必需的。引人注目的是，crol 的持续过度表达将 bwD 的斑点杂色模式转化为扇形杂色，其中去抑制通过有丝分裂稳定遗传。 croll 的过度表达会建立开放染色质状态，但不需要该因子来维持这种状态。我们的分析表明，活跃的染色质状态可以通过细胞分裂有效遗传，这对发育过程中基因表达模式的稳定维持具有影响。重复的 DNA 和转座子被压缩成真核基因组中的异染色质，以沉默潜在的危险元素。异染色质沉默与经典的基因抑制不同，因为受影响的基因在发育过程中随机打开和关闭，具有不同程度的体细胞遗传性。在这里，我们重点关注同源染色体上重复 DNA 卫星块对报告基因的沉默。该系统中的沉默依赖于长程染色体相互作用，但这些相互作用在有丝分裂过程中被破坏，并且必须在每个细胞周期中重新建立。我们采用诱导系统来识别过度表达时可以改变沉默的因素。该系统的诱导性质使我们能够扰乱不同发育阶段的沉默，并区分影响沉默建立或维持的因素。我们鉴定了多种修饰剂，大多数修饰剂甚至可以在分化细胞中改变沉默的染色质。引人注目的是，一种因子——crol 锌指蛋白——的过度表达会建立一种体细胞遗传的去抑制状态。我们对crol的分析表明细胞周期进展与沉默染色质的维持有关，并认为活跃的染色质可以通过有丝分裂有效地繁殖。我们的研究结果验证了诱导修饰剂作为解析染色质状态建立和维持的工具。
Repetitive sequences in eukaryotic genomes induce chromatin-mediated gene-silencing of juxtaposed genes. Many components that promote or antagonize silencing have been identified, but how heterochromatin causes variegated and heritable changes in gene expression remains mysterious. We have used inducible mis-expression in the Drosophila eye to recover new factors that alter silencing caused by the bwD allele, an insertion of repetitive satellite DNA that silences a bw+ allele on the homologous chromosome. Inducible modifiers allow perturbation of silencing at different times in development, and distinguish factors that affect establishment or maintenance of silencing. We find that diverse chromatin and RNA processing factors can de-repress silencing. Most factors are effective even in differentiated cells, implying that silent chromatin remains plastic. However, over-expression of the bantam microRNA or the crooked-legs (crol) zinc-finger protein only de-repress silencing when expressed in cycling cells. Over-expression of crol accelerates the cell cycle, and this is required for de-repression of silencing. Strikingly, continual over-expression of crol converts the speckled variegation pattern of bwD into sectored variegation, where de-repression is stably inherited through mitotic divisions. Over-expression of crol establishes an open chromatin state, but the factor is not needed to maintain this state. Our analysis reveals that active chromatin states can be efficiently inherited through cell divisions, with implications for the stable maintenance of gene expression patterns through development. Repetitive DNA and transposons are compacted into heterochromatin in eukaryotic genomes to silence potentially dangerous elements. Heterochromatic silencing is distinct from classical gene repression because affected genes randomly switch on and off during development, with varying degrees of somatic heritability. Here, we focus on the silencing of a reporter gene by a repetitive DNA satellite block on a homologous chromosome. Silencing in this system relies on long-range chromosomal interactions, but these are disrupted during mitosis and must be re-established every cell cycle. We employed an inducible system to identify factors that can alter silencing when over-expressed. The inducible nature of this system allows us to perturb silencing at different development stages, and distinguish factors that affect the establishment or maintenance of silencing. We identified a diverse collection of modifiers, and most can alter silenced chromatin even in differentiating cells. Strikingly, over-expression of one factor – the crol zinc-finger protein – establishes a de-repressed state that is somatically heritable. Our analysis of crol implicates cell cycle progression in the maintenance of silenced chromatin, and argues that active chromatin can be efficiently propagated through mitotic divisions. Our findings validate inducible modifiers as tools for the dissection of establishment and maintenance of chromatin states.
登录
查看更多内容
影响因子：
56.9
作者：
DENOOIJ, JC;HARIHARAN, IK
通讯作者：
HARIHARAN, IK
影响因子：
64.5
作者：
Ahmad, K;Henikoff, S
通讯作者：
Henikoff, S
影响因子：
64.5
作者：
Freeman, M
通讯作者：
Freeman, M
影响因子：
64.5
作者：
Cavalli, G;Paro, R
通讯作者：
Paro, R
影响因子：
64.5
作者：
GROUDINE, M;WEINTRAUB, H
通讯作者：
WEINTRAUB, H