Identification And Characterization Of Human Rsc Chromat

atp依赖性染色质重塑复合体（Rsc）最初是在酵母中发现的。它的亚基组成与表征良好的SWI/SNF相似：两个配合物共有2个亚基，另外至少有4个亚基相互同源。然而，Rsc的功能不同于SWI/SNF。Rsc是酵母有丝分裂生长所必需的，而SWI/SNF则不是。Rsc突变体在细胞周期的G2/M转变中被捕获，并且这种捕获依赖于纺锤体检查点基因。突变体对破坏微管稳定的药物也更敏感。这些数据表明Rsc可能在有丝分裂中发挥作用，可能通过稳定有丝分裂纺锤体形成或在着丝点上起作用。我们之前已经从人体内纯化了几种atp依赖性染色质重塑复合物，这些复合物与酵母SWI/SNF或Rsc密切相关。通过微测序和克隆，我们鉴定出人类SWI/SNF-B复合物的BAF180亚基与酵母Rsc亚基Rsc1、Rsc2和Rsc4具有同源性。它具有与三个Rsc亚基相同的生化基序：6个溴结构域，2个BAH区域和一个小槽结合结构域。对已完成的人类、果蝇和C.elegance基因组数据库进行数据库检索，发现BAF180是三个Rsc亚基最接近的同源物，提示人类SWI/SNF-B是人类版本的Rsc。我们随后鉴定了人类Rsc复合物的许多其他亚基，并发现其中许多亚基与人类SWI/SNF中的亚基相同。我们还证明了BAF180定位于有丝分裂染色体的着丝点，这与有丝分裂过程中Rsc的功能一致。这项工作最近发表在PNAS （PMID: 11078522）上。我们目前正在努力确定人类SWI/SNF-B的剩余成分。在未来，我们将尝试识别受该复合体调节的基因。

The ATP-dependent Chromatin-remodeling complex, Rsc, was originally identified in yeast. It has a subunit composition similar to the well-characterized SWI/SNF: 2 subunits are shared between the two complexes and at least 4 others are homologues of each other. However, the function of Rsc is distinct from SWI/SNF. Rsc is essential for the mitotic growth of yeast, whereas SWI/SNF is not. Rsc mutants are arrested at G2/M transition during the cell cycle, and the arrest is dependent on spindle-checkpoint genes. The mutants are also more sensitive to microtubule- destabilizing drugs. These data suggest that Rsc may play a role in mitosis, perhaps by stabilizing mitotic spindle formation or have a function at kinetochores. We have previously purified several ATP-dependent chromatin remodeling complexes from human that are closely related to either yeast SWI/SNF or Rsc. By microsequencing and cloning, we now identified the BAF180 subunit of human SWI/SNF-B complex as a human homologue of yeast Rsc subunits, Rsc1, Rsc2 and Rsc4. It has the same set of biochemical motifs as the three Rsc subunits: 6 bromodomains, 2 BAH regions, and a minor-groove binding domain. Database search of the completed genome database of human, Drosophila and C.elegance showed that BAF180 is the closest homolog of the three Rsc subunits, suggesting human SWI/SNF-B as a human version of Rsc. We subsequently identified many other subunits of human Rsc complex and found a number of them to be identical to those in human SWI/SNF. We also demonstrated that BAF180 localizes at kinetochores of mitotic chromosomes, consistent with a function for Rsc during mitosis. This work has recently been published in PNAS (PMID: 11078522). We are currently trying to identify the remaining components of human SWI/SNF-B. In the future, we will try to identify genes that are regulated by this complex.