Integrity of the Mod(mdg4)-67.2 BTB domain is critical to insulator function in Drosophila melanogaster.
The Drosophila gypsy insulator contains binding sites for the Suppressor of Hairy-wing [Su(Hw)] protein. Enhancer and silencer blocking require Su(Hw) recruitment of Mod(mdg4)-67.2, a BTB/POZ domain protein that interacts with Su(Hw) through a carboxyl-terminal acidic domain. Here we conducted mutational analyses of the Mod(mdg4)-67.2 BTB domain. We demonstrate that this domain is essential for insulator function, in part through direction of protein dimerization. Our studies revealed the presence of a second domain (DD) that contributes to Mod(mdg4)-67.2 dimerization when the function of the BTB domain is compromised. Additionally, we demonstrate that mutations in amino acids of the charged pocket in the BTB domain that retain dimerization of the mutated protein cause a loss of insulator function. In these cases, the mutant proteins failed to localize to chromosomes, suggesting a role for the BTB domain in chromosome association. Interestingly, replacement of the Mod(mdg4)-67.2 BTB domain with the GAF BTB domain produced a nonfunctional protein. Taken together, these data suggest that the Mod(mdg4)-67.2 BTB domain confers novel activities to gypsy insulator function.
Golovnin
Anton
A
Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow 119334, Russia.
Mazur
Alexander
A
Kopantseva
Marina
M
Kurshakova
Maria
M
Gulak
Pavel V
PV
Gilmore
Brian
B
Whitfield
William G F
WG
Geyer
Pamela
P
Pirrotta
Vincenzo
V
Georgiev
Pavel
P
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002875:Chromosomes / Q000378:metabolism; D004252:DNA Mutational Analysis; D019281:Dimerization; D004171:Diploidy; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D038101:Insulator Elements / Q000235:genetics*; D007814:Larva / Q000166:cytology; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014921:Wings, Animal / Q000166:cytology / Q000473:pathology
C107964:CP190 protein, Drosophila; D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; D050505:Mutant Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C101384:mod(mdg4) protein, Drosophila