'Insulator bodies' are aggregates of proteins but not of insulators.

Chromatin insulators are thought to restrict the action of enhancers and silencers. The best-known insulators in Drosophila require proteins such as Suppressor of Hairy wing (Su(Hw)) and Modifier of mdg4 (Mod(mdg4)) to be functional. The insulator-related proteins apparently colocalize as nuclear speckles in immunostained cells. It has been asserted that ...
these speckles are 'insulator bodies' of many Su(Hw)-insulator DNA sites held together by associated proteins, including Mod(mdg4). As we show here using flies, larvae and S2 cells, a mutant Mod(mdg4) protein devoid of the Q-rich domain supports the function of Su(Hw)-dependent insulators and efficiently binds to correct insulator sites on the chromosome, but does not form or enter the Su(Hw)-marked nuclear speckles; conversely, the latter accumulate another (C-truncated) Mod(mdg4) mutant that cannot interact with Su(Hw) or with the genuine insulators. Hence, it is not the functional genomic insulators but rather aggregated proteins that make the so-called 'insulator bodies'.
Mesh Terms:
Alleles, Animals, DNA-Binding Proteins, Drosophila, Drosophila Proteins, Embryo, Nonmammalian, Immunohistochemistry, Insulator Elements, Larva, Male, Mutation, Nuclear Proteins, Protein Structure, Tertiary, Recombinant Proteins, Repressor Proteins, Transcription Factors, Transgenes, Wings, Animal
EMBO Rep.
Date: May. 01, 2008
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