COHESIN COMPLEX

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 粘附素复合体在复制后将姐妹染色单体结合在一起，直到中期和后期。它由脊椎动物的四个核心蛋白亚基组成，即Rad21、SMC1、SMC3、SCC3(SA1、SA2)。粘附素复合体的质量约为600 kDa。当一个粘附素亚基--SCc1/Rad21-被一种称为分离酶的内肽酶切割时，姐妹染色单体就会被撕裂。粘附素成分的突变可能导致姐妹染色单体分离的延迟、过早和/或完全抑制，并导致非整倍体。SMC1和SMC3的N-末端和C-末端都是ABC样ATPase，而中心区域是铰链结构域，形成反平行的分子内卷曲。SMC1和SMC3也通过铰链结构域形成二聚体。通过金属阴影，SMC1-SMC3二聚体看起来像一个开环。SMC1-SMC3杂二聚体的臂长度约为60 nm。从对发芽酵母的研究中得出的粘附素环模型似乎是合理的(Gruber等人，2003年细胞112,765-777)。这表明SCC1/Rad21C-末端和N-末端分别与SMC1和SMC3异源二聚体的ATPase头部结合，形成一个三角环。然后，SCC3结合以加强环。姐妹染色单体被环包围(Uhlmann，2004，Exp.Cell Res.296，80-85)。然而，根据EM数据，如果三角形环可以变成一个圆，那么环的最大直径小于35 nm，不足以容纳两个30 nm的姐妹染色单体。我们研究了人类细胞系中粘附素亚基之间的蛋白质-蛋白质相互作用。我们的结果表明，粘附素复合体不是一个简单的环。为了确认我们的生化结果，我们正在用低温电子显微镜观察这个复合体。我们的目标是解决粘附素复合体的三维结构，并揭示粘附素复合体如何与DNA相互作用

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The cohesin complex holds the sister chromatids together after replication until metaphase and anaphase. It is composed of four core protein subunits in vertebrates, Rad21, SMC1, SMC3, SCC3 (SA1, SA2). The mass of cohesin complex is about 600 kDa. Sister chromatids are pulled apart when one cohesin subunit - SCC1/Rad21 - is cleaved by an endopeptidase called separase. Mutation of cohesin components may lead to delayed, premature and/or total inhibition of sister chromatid separation and result in aneuploidy. The N- and C-termini of both the SMC1 and SMC3 components are ABC-like ATPases , while the central region is a hinge domain, forming antiparallel intramolecular coiled coils. SMC1 and SMC3 also form a dimer via the hinge domain. The SMC1-SMC3 dimer looks like an open loop by metal-shadowing. The length of the SMC1-SMC3 heterodimer arm is about 60 nm. A cohesin ring model derived from studies on budding yeast seems reasonable (Gruber et al., 2003 Cell 112, 765-777). It suggests that SCC1/Rad21 C- and N-terminus bind to the ATPase heads of SMC1 and SMC3 heterodimer, respectively, to form a triangular ring. SCC3 then binds to reinforce the ring. Sister chromatids are surrounded by the ring (Uhlmann, 2004, Exp.Cell Res. 296, 80-85). However, according to the EM data, the maximum diameter of the ring is less than 35nm if the triangular ring can become a circle, which is not big enough to hold two 30 nm sister chromatids. We have studied the protein-protein interactions among the cohesin subunits in human cell lines. Our results indicate that cohesin complex is not a simple ring. To confirm our biochemical results, we are visualizing the complex by cryoEM. Our goal is to solve the 3-D structure of cohesin complex and to reveal how cohesin complex interact with DNA