Kato Masaki, Kato Yasuko, Nishida Miki, Hayakawa Tomohiro, Haraguchi Tokuko, Hiraoka Yasushi, H Inoue Yoshihiro, Yamaguchi Masamitsu
Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan.
Cell Struct Funct. 2007;32(1):57-67. doi: 10.1247/csf.06032. Epub 2007 Jun 18.
Three subtypes of HP1, a conserved non-histone chromosomal protein enriched in heterochromatin, have been identified in humans, HP1alpha, beta and gamma. In the present study, we utilized a Drosophila system to characterize human HP1 functions. Over-expression of HP1beta in eye imaginal discs caused abnormally patterned eyes, with reduced numbers of ommatidia, and over-expression of HP1gamma in wing imaginal discs caused abnormal wings, in which L4 veins were gapped. These phenotypes were specific to the HP1 subtypes and appear to reflect suppressed gene expression. To determine the molecular domains of HP1 required for each specific phenotype, we constructed a series of chimeric molecules with HP1beta and HP1gamma. Our data show that the C-terminal chromo shadow domain (CSD) of HP1gamma is necessary for HP1gamma-type phenotype, whereas for the HP1beta-type phenotype both the chromo domain and the CSD are required. These results suggest human HP1 subtypes use different domains to suppress gene expression in Drosophila cells.
异染色质中富集的一种保守的非组蛋白染色体蛋白HP1在人类中有三种亚型，即HP1α、β和γ。在本研究中，我们利用果蝇系统来表征人类HP1的功能。在眼成虫盘过表达HP1β导致眼睛图案异常，小眼数量减少，而在翅成虫盘过表达HP1γ导致翅膀异常，其中L4翅脉有间隙。这些表型是HP1亚型特有的，似乎反映了基因表达受到抑制。为了确定每种特定表型所需的HP1分子结构域，我们构建了一系列HP1β和HP1γ的嵌合分子。我们的数据表明，HP1γ的C端染色质影域（CSD）对于HP1γ型表型是必需的，而对于HP1β型表型，染色质域和CSD都是必需的。这些结果表明，人类HP1亚型在果蝇细胞中利用不同的结构域来抑制基因表达。
