Heterochromatin biology

我们正在研究的机制，保持组成异染色质区在一个浓缩的形式。为了这个目的，我们最初使用了一个很好的特点，16 kb的异染色质片段位于鸡β珠蛋白基因座的上游。在其他已发表的研究中，我们测量了该片段的流体动力学特性，这是大部分脊椎动物基因组的典型特征，如果不受调节，则有可能以有害于细胞功能的方式使相邻基因沉默。我们发现，凝聚结构的维护耦合到低水平的转录在该地区，和组蛋白乙酰化水平的升高，通过使用组蛋白去乙酰化酶抑制剂（TSA）显着增加转录。我们问是否Dicer/Argonaute依赖机制可能参与形成这个异染色质区域。我们发现，通过siRNA消耗Dicer导致浓缩的染色质结构的开放，与TSA处理后观察到的情况非常相似。此外，Ago 2以Dicer依赖性方式结合到该区域。 我们现在已经研究了Ago 2与人红细胞系K562中核糖体基因重复序列的结合。我们发现人AGO 2定位于rRNA基因编码区的染色质。 这种定位是通过与影响rRNA修饰的RNA相互作用介导的。

We are studying the mechanisms that maintain constitutive heterochromatic regions in a condensed form. For this purpose we originally used a well characterized 16 kb heterochromatin segment located upstream of the chicken beta globin locus. In other published studies we have measured the hydrodynamic properties of this fragment, which is typical of a large proportion of vertebrate genomes, and which has the potential if unregulated to silence adjacent genes in a manner deleterious to cellular function. We found that maintenance of the condensed structure is coupled to low level transcription in the region, and that elevation of levels of histone acetylation by use of histone deacetylase inhibitors (TSA) markedly increases transcription. We asked whether Dicer/Argonaute dependent mechanisms could be involved in formation of this heterochromatic region. We found that depletion of Dicer by siRNA resulted in opening of the condensed chromatin structure much as what was observed following TSA treatment. Furthermore, Ago2 is bound to this region in a Dicer-dependent manner. We have now investigated the binding of Ago2 to the ribosomal gene repeats in the human erythroid cell line, K562. We find that human AGO2 is localized to the chromatin of the rRNA gene coding region. This localization is mediated through interaction with RNAs that affect rRNA modification.