Gene Expression Programme,
EMBL, Meyerhofstrasse 1,
D-69117 Heidelberg. Germany
Published in: Nucleic Acids Research 23(16): 3168-3173 (1995)
The chromo domain was originally identified as a protein sequence motif common to the Drosophila chromatin proteins, Polycomb (Pc) and Heterochromatin protein 1 (HP1). 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 domai n, 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 ex amples of proteins which have two classical chromo domains. The S. 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 SpSWI6, HP1 and HP1-like proteins sup ports the model that the specificity of action of chromatin proteins is generated by combinations of protein modules.
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This work was carried out at the EMBL and partly at the University of Bergen.
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