Tang Yong, Poustovoitov Maxim V, Zhao Kehao, Garfinkel Megan, Canutescu Adrian, Dunbrack Roland, Adams Peter D, Marmorstein Ronen
The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
Nat Struct Mol Biol. 2006 Oct;13(10):921-9. doi: 10.1038/nsmb1147. Epub 2006 Sep 17.
Human HIRA, ASF1a, ASF1b and CAF-1 are evolutionally conserved histone chaperones that form multiple functionally distinct chromatin-assembly complexes, with roles linked to diverse nuclear process, such as DNA replication and formation of heterochromatin in senescent cells. We report the crystal structure of an ASF1a-HIRA heterodimer and a biochemical dissection of ASF1a's mutually exclusive interactions with HIRA and the p60 subunit of CAF-1. The HIRA B domain forms an antiparallel beta-hairpin that binds perpendicular to the strands of the beta-sandwich of ASF1a, via beta-sheet, salt bridge and van der Waals contacts. The N- and C-terminal regions of ASF1a and ASF1b determine the different affinities of these two proteins for HIRA, by contacting regions outside the HIRA B domain. CAF-1 p60 also uses B domain-like motifs for binding to ASF1a, thereby competing with HIRA. Together, these studies begin to define the molecular determinants of assembly of functionally diverse macromolecular histone chaperone complexes.
人类HIRA、ASF1a、ASF1b和CAF-1是进化上保守的组蛋白伴侣，它们形成多种功能不同的染色质组装复合物，其作用与多种核过程相关，如DNA复制和衰老细胞中异染色质的形成。我们报道了ASF1a-HIRA异二聚体的晶体结构，以及对ASF1a与HIRA和CAF-1的p60亚基相互排斥相互作用的生化分析。HIRA B结构域形成一个反平行β-发夹，通过β-折叠、盐桥和范德华接触垂直结合到ASF1a的β-三明治结构的链上。ASF1a和ASF1b的N端和C端区域通过与HIRA B结构域之外的区域接触，决定了这两种蛋白质对HIRA的不同亲和力。CAF-1 p60也使用类似B结构域的基序与ASF1a结合，从而与HIRA竞争。这些研究共同开始定义功能多样的大分子组蛋白伴侣复合物组装的分子决定因素。
