Kamata Kazuma, Shinmyozu Kaori, Nakayama Jun-Ichi, Hatashita Masanori, Uchida Hiroyuki, Oki Masaya
Department of Applied Chemistry Biotechnology, Graduate School of Engineering, University of Fukui, Bunkyo, Fukui, Japan.
Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan.
Genes Cells. 2016 Oct;21(10):1125-1136. doi: 10.1111/gtc.12421. Epub 2016 Sep 20.
In eukaryotic cells, there are two chromatin states, silenced and active, and the formation of a so-called boundary plays a critical role in demarcating these regions; however, the mechanisms underlying boundary formation are not well understood. In this study, we focused on S. cerevisiae ADA1, a gene previously shown to encode a protein with a robust boundary function. Ada1 is a component of the histone modification complex Spt-Ada-Gcn5-acetyltransferase (SAGA) and the SAGA-like (SLIK) complex, and it helps to maintain the integrity of these complexes. Domain analysis showed that four relatively small regions of Ada1 (Region I; 66-75 aa, II; 232-282 aa, III; 416-436 aa and IV; 476-488 aa) have a boundary function. Among these, Region II could form an intact SAGA complex, whereas the other regions could not. Investigation of cellular factors that interact with these small regions identified a number of proteasome-associated proteins. Interestingly, the boundary functions of Region II and Region III were affected by depletion of Ump1, a maturation and assembly factor of the 20S proteasome. These results suggest that the boundary function of Ada1 is functionally linked to proteasome processes and that the four relatively small regions in ADA1 form a boundary via different mechanisms.
在真核细胞中，存在沉默和活跃两种染色质状态，所谓边界的形成在划分这些区域中起着关键作用；然而，边界形成的潜在机制尚未完全了解。在本研究中，我们聚焦于酿酒酵母ADA1，该基因先前已被证明编码一种具有强大边界功能的蛋白质。Ada1是组蛋白修饰复合物Spt-Ada-Gcn5-乙酰转移酶（SAGA）和类SAGA（SLIK）复合物的组成部分，它有助于维持这些复合物的完整性。结构域分析表明，Ada1的四个相对较小的区域（区域I；66 - 75个氨基酸，II；232 - 282个氨基酸，III；416 - 436个氨基酸和IV；476 - 488个氨基酸）具有边界功能。其中，区域II能够形成完整的SAGA复合物，而其他区域则不能。对与这些小区域相互作用的细胞因子的研究鉴定出了许多与蛋白酶体相关的蛋白质。有趣的是，区域II和区域III的边界功能受到Ump1（20S蛋白酶体的成熟和组装因子）缺失的影响。这些结果表明，Ada1的边界功能在功能上与蛋白酶体过程相关联，并且ADA1中的四个相对较小的区域通过不同机制形成边界。
