An Sojin, Kim Hanseong, Cho Uhn-Soo
Department of Biological Chemistry, University of Michigan Medical School, 1150 West Medical Center Drive, SPC 5606, Ann Arbor, MI 48109, USA.
Department of Biological Chemistry, University of Michigan Medical School, 1150 West Medical Center Drive, SPC 5606, Ann Arbor, MI 48109, USA.
J Mol Biol. 2015 Oct 9;427(20):3230-3240. doi: 10.1016/j.jmb.2015.08.022. Epub 2015 Sep 4.
CENP-A is a centromere-specific histone H3 variant that is required for kinetochore assembly and accurate chromosome segregation. For it to function properly, CENP-A must be specifically localized to centromeres. In fission yeast, Scm3sp and the Mis18 complex, composed of Mis16, Eic1, and Mis18, function as a CENP-A(Cnp1)-specific chaperone and a recruiting factor, respectively, and together ensure accurate delivery of CENP-A(Cnp1) to centromeres. Although how Scm3sp specifically recognizes CENP-A(Cnp1) has been revealed recently, the recruiting mechanism of CENP-A(Cnp1) via the Mis18 complex remains unknown. In this study, we have determined crystal structures of Schizosaccharomyces japonicus Mis16 alone and in complex with the helix 1 of histone H4 (H4α1). Crystal structures followed by mutant analysis and affinity pull-downs have revealed that Mis16 recognizes both H4α1 and Scm3sp independently within the CENP-A(Cnp1)/H4:Scm3sp complex. This observation suggests that Mis16 gains CENP-A(Cnp1) specificity by recognizing both Scm3sp and histone H4. Our studies provide insights into the molecular mechanisms underlying specific recruitment of CENP-A(Cnp1)/H4:Scm3sp into centromeres.
着丝粒蛋白A(CENP - A)是一种着丝粒特异性组蛋白H3变体,是动粒组装和精确染色体分离所必需的。为了正常发挥功能,CENP - A必须特异性定位于着丝粒。在裂殖酵母中,Scm3sp以及由Mis16、Eic1和Mis18组成的Mis18复合体分别作为CENP - A(Cnp1)特异性伴侣蛋白和募集因子,共同确保CENP - A(Cnp1)准确递送至着丝粒。尽管最近已经揭示了Scm3sp如何特异性识别CENP - A(Cnp1),但通过Mis18复合体募集CENP - A(Cnp1)的机制仍然未知。在本研究中,我们确定了日本裂殖酵母Mis16单独以及与组蛋白H4的螺旋1(H4α1)形成复合体时的晶体结构。通过晶体结构分析、突变分析和亲和下拉实验表明,在CENP - A(Cnp1)/H4:Scm3sp复合体中,Mis16独立识别H4α1和Scm3sp。这一观察结果表明,Mis16通过识别Scm3sp和组蛋白H4获得了CENP - A(Cnp1)特异性。我们的研究为CENP - A(Cnp1)/H4:Scm3sp特异性募集到着丝粒的分子机制提供了见解。