The core-promoter factor TRF2 mediates a Fruitless action to masculinize neurobehavioral traits in Drosophila

In fruit flies, the male-specific fruitless ( fru ) gene product FruBM plays a central role in establishing the neural circuitry for male courtship behavior by orchestrating the transcription of genes required for the male-type specification of individual neurons. We herein identify the core promoter recognition factor gene Trf2 as a dominant modifier of fru actions. Trf2 knockdown in the sexually dimorphic mAL neurons leads to the loss of a male-specific neurite and a reduction in male courtship vigor. TRF2 forms a repressor complex with FruBM, strongly enhancing the repressor activity of FruBM at the promoter region of the robo1 gene, whose function is required for inhibiting the male-specific neurite formation. In females that lack FruBM, TRF2 stimulates robo1 transcription. Our results suggest that TRF2 switches its own role from an activator to a repressor of transcription upon binding to FruBM, thereby enabling the ipsilateral neurite formation only in males. fruitless ( fru ) is an important sex-determinant gene that controls the expression of neuroanatomical sex differences in Drosophila . Here the authors report that a core-promoter factor, TRF2, suppresses a male-type neurite specification through direct interaction with FruBM isoform at the robo1 target gene promoter.