Complex formation by the Drosophila MSL proteins: role of the MSL2 RING finger in protein complex assembly.
Drosophila MSL proteins are thought to act within a complex to elevate transcription from the male X chromosome. We found that the MSL1, MSL2 and MSL3 proteins are associated in immunoprecipitations, chromatographic steps and in the yeast two-hybrid system, but that the MLE protein is not tightly complexed in these assays. We focused our analysis on the MSL2-MSL1 interaction, which is postulated to play a critical role in MSL complex association with the X chromosome. Using a modified two-hybrid assay, we isolated missense mutations in MSL2 that disrupt its interaction with MSL1. Eleven out of 12 mutated residues clustered around the first zinc-binding site of the RING finger domain were conserved in a Drosophila virilis MSL2 homolog. Two pre-existing msl2 alleles, which fail to support male viability in vivo, have lesions in the same region of the RING finger. We tested these in the two-hybrid system and found that they are also defective in interaction with MSL1. Mutation of the second zinc-binding site had little effect on MSL1 binding, suggesting that this portion of the RING finger may have a distinct function. Our data support a model in which MSL2-MSL1 interaction nucleates assembly of an MSL complex, with which MLE is weakly or transiently associated.
Copps
K
K
Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Richman
R
R
Lyman
L M
LM
Chang
K A
KA
Rampersad-Ammons
J
J
Kuroda
M I
MI
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone; D017124:Conserved Sequence; D004265:DNA Helicases; D004268:DNA-Binding Proteins; D004303:Dosage Compensation, Genetic; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D046911:Macromolecular Substances; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D020365:RNA Helicases / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016335:Zinc Fingers
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C070837:mle protein, Drosophila; C082132:msl-1 protein, Drosophila; C094166:msl-2 protein, Drosophila; C093904:msl-3 protein, Drosophila; D004265:DNA Helicases; D020365:RNA Helicases