'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'.
Golovnin
Anton
A
Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, Moscow 119334, Russia.
Melnikova
Larisa
L
Volkov
Ilya
I
Kostuchenko
Margarita
M
Galkin
Alexander V
AV
Georgiev
Pavel
P
D000483:Alleles; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004330:Drosophila / Q000166:cytology / Q000196:embryology / Q000235:genetics; D029721:Drosophila Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian; D007150:Immunohistochemistry; D038101:Insulator Elements; D007814:Larva; D008297:Male; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes; D014921:Wings, Animal / Q000196:embryology
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C110987:mdg4 protein (gypsy); C083738:su(Hw) protein, Drosophila