<i>Drosophila melanogaster</i> MLE Helicase functions beyond dosage compensation: molecular nature and pleiotropic effect of <i>mle[9]</i>

MLE of D. melanogaster is a conserved protein in higher eukaryotes, an ortholog of human DHX9 helicase. In mammals, this helicase has been shown to participate in different stages of gene expression. In D. melanogaster, the role of MLE as one of the components of the species-specific Dosage Compensation Complex has been extensively studied. However, the role of MLE in other processes has remained poorly understood. In this work, for the first time, the mle[9] mutation is mapped at the molecular level and shown to be caused by a deletion resulting in the loss of a highly conserved motif III in the catalytic core of the molecule. Thus, mle[9] specifically disrupts the helicase activity of the protein without affecting the function of other domains. The study of phenotypic manifestations of the mutation in females showed that in the homozygous state it has a pleiotropic effect. Without affecting survival, it significantly reduces fertility and lifespan. In addition, the duplication of scutellar macrochaetae was observed with high frequency. These results confirm that in D. melanogaster MLE helicase is involved in a wide range of gene expression regulation processes distinct from its role in dosage compensation.