Initiative for the Promotion of Young Scientists' Independent Research, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba 305-8577, Japan.
Genes Cells. 2010 Jan;15(1):13-27. doi: 10.1111/j.1365-2443.2009.01361.x. Epub 2009 Dec 9.
Nucleosome Assembly Protein 1 (NAP1) is a highly conserved histone chaperone protein suspected to be involved in the dynamical regulation of the histone H2A-H2B hetero-dimer. However, the exact mechanism by which NAP1-like proteins act is currently unknown. In this work, we characterized the biochemical properties of two human NAP1-like proteins, hNAP1L1 and hNAP1L4, including a previously uncharacterized subtype, with the aim of determining their exact mechanistic role. Both hNAP1L1 and hNAP1L4 were found to be localized mainly to the cytoplasm and a minor population of them was suggested to be in the nucleus. Biochemical analyses demonstrated that both hNAP1L1 and hNAP1L4 mediated nucleosome formation. In addition, hNAP1L1 was shown to possess a significantly greater nucleosome disassembly activity than hNAP1L4, suggesting that hNAP1L1 and hNAP1L4 may play distinct roles in the regulation of histone dynamics. Building upon this initial discovery we also found that histone H2A-H2B and various histone H2A variants-H2B dimers were found to associate with both hNAP1L1 and hNAP1L4 in cell extracts. These results suggest that human NAP1-like proteins play overlapping roles in transport and deposition of histone H2A-H2B or H2A variants-H2B dimers on chromatin and nonoverlapping roles in nucleosome disassembly.
核小体组装蛋白 1（NAP1）是一种高度保守的组蛋白伴侣蛋白，据推测其参与了组蛋白 H2A-H2B 异二聚体的动态调节。然而，NAP1 样蛋白的确切作用机制目前尚不清楚。在这项工作中，我们对两种人类 NAP1 样蛋白（hNAP1L1 和 hNAP1L4）的生化特性进行了表征，包括一种以前未被描述的亚型，旨在确定它们的确切作用机制。发现 hNAP1L1 和 hNAP1L4 主要定位于细胞质中，而一小部分则存在于细胞核中。生化分析表明，hNAP1L1 和 hNAP1L4 均介导核小体的形成。此外，hNAP1L1 显示出比 hNAP1L4 更强的核小体解体活性，表明 hNAP1L1 和 hNAP1L4 可能在组蛋白动力学调节中发挥不同的作用。基于这一初步发现，我们还发现组蛋白 H2A-H2B 和各种组蛋白 H2A 变体-H2B 二聚体在细胞提取物中与 hNAP1L1 和 hNAP1L4 均有结合。这些结果表明，人类 NAP1 样蛋白在组蛋白 H2A-H2B 或 H2A 变体-H2B 二聚体在染色质上的运输和沉积中发挥重叠作用，而在核小体解体中发挥非重叠作用。
