Aasland R, Stewart A F
Gene Expression Programme, EMBL, Heidelberg, Germany.
Nucleic Acids Res. 1995 Aug 25;23(16):3168-73. doi: 10.1093/nar/23.16.3168.
The chromo domain was originally identified as a protein sequence motif common to the Drosophila chromatin proteins, Polycomb (Pc) and heterochromatin protein 1 [HP1; Paro and Hogness (1991) Proc. Natl. Acad. Sci. USA, 88, 263-267; Paro (1990) Trends Genet., 6, 416-421]. Here we describe a second chromo domain-like motif in HP1. Subsequent refined searches identified further examples of this chromo domain variant which all occur in proteins that also have an N-terminally located chromo domain. Due to its relatedness to the chromo domain, and its occurrence in proteins that also have a classical chromo domain, we call the variant the 'chromo shadow domain'. Chromo domain-containing proteins can therefore be divided into two classes depending on the presence, for example in HP1, or absence, for example in Pc, of the chromo shadow domain. We have also found examples of proteins which have two classical chromo domains. The Schizosaccharomyces pombe SWI6 protein, involved in repression of the silent mating-type loci, is a member of the chromo shadow group. The similar modular architecture of SpSW16, HP1 and HP1-like proteins supports the model that the specificity of action of chromatin proteins is generated by combinations of protein modules.
染色体结构域最初被鉴定为果蝇染色质蛋白多梳蛋白（Pc）和异染色质蛋白1 [HP1；帕罗和霍格尼斯（1991年）《美国国家科学院院刊》，88卷，263 - 267页；帕罗（1990年）《遗传学趋势》，6卷，416 - 421页] 中常见的蛋白质序列基序。在此，我们描述了HP1中第二个类似染色体结构域的基序。随后的精细搜索发现了这种染色体结构域变体的更多实例，它们均出现在同样具有位于N端的染色体结构域的蛋白质中。由于其与染色体结构域的相关性，以及在同样具有经典染色体结构域的蛋白质中的出现，我们将该变体称为“染色体影子结构域”。因此，含有染色体结构域的蛋白质可根据例如在HP1中存在或在Pc中不存在染色体影子结构域分为两类。我们还发现了具有两个经典染色体结构域的蛋白质实例。参与沉默交配型基因座抑制的粟酒裂殖酵母SWI6蛋白是染色体影子蛋白组的成员。SpSWI6、HP1和类HP1蛋白相似的模块化结构支持了染色质蛋白作用特异性由蛋白质模块组合产生的模型。
