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

Abstract

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.

The mode of action of Fruitless: Is it an easy matter to switch the sex?

“…What is interesting, however, is the result of the reporter assay with the robo1 promoter fragment in transfected S2 cells: TRF2 activates transcription when applied singly, but when applied together with a low concentration of FruBM that is insufficient for transcription repression, TRF2 actually represses transcription-that is, TRF2 now potentiates the FruM repressor action. 41 This finding raises the intriguing possibility that local interactions of FruBM with TRF2 on the robo1 promoter might underlie the context-dependent switching between activation and repression of robo1 transcription.…”

“…Genetic screens for phenotypic fru modifiers identified TATA-box-binding protein-related factor 2 (TRF2), 41 which is known as a transcriptional activator that preferentially binds to the core promoter sequence with a TCT motif. 41 This finding raises the intriguing possibility that local interactions of FruBM with TRF2 on the robo1 promoter might underlie the context-dependent switching between activation and repression of robo1 transcription. As expected, the robo1 promoter fragment with TCT and DREAM motifs binds TRF2.…”

“…The robo1 gene promoter offers an unparalleled opportunity to dis- Figure 3C). Genetic screens for phenotypic fru modifiers identified TATA-box-binding protein-related factor 2 (TRF2), 41 which is known as a transcriptional activator that preferentially binds to the core promoter sequence with a TCT motif. 42,43 DNA replication-related element-binding factor (DREF), a known binding partner of TRF2, binds to DRE, 44 whose palindrome repeat is contained in a DREAM motif.…”

Sex Mysteries of the Fly Courtship Master Regulator Fruitless

“…The 101 a.a. extension unique to FruM proteins has no known motif, whereas the main body of the protein has a BTB domain near the N-terminus and two zinc finger motifs at the C-terminus (Ito et al, 1996; Ryner et al, 1996; Figure 1D). The BTB-Zn finger proteins are dominated by transcriptional regulators, and indeed, this proved to be true for FruM as well; FruBM binds to the DNA region named FROS to repress transcription of a target gene (e.g., robo1 , Ito et al, 2016) that forms a complex with other transcription regulators, including HDAC1, HP1a, Bonus, TRF2 and Lola (Ito et al, 2012; Chowdhury et al, 2017; Sato et al, 2019), some of which are well known for their involvement in chromatin modifications. Although C-terminal variations likely contribute to target specificities (Neville et al, 2014; von Philipsborn et al, 2014), the absence of the male-specific N-terminal extension probably does not narrow the range of target choice, because major portions of the behavioral and cellular phenotypes of FruM-null mutants are rescuable by artificial expression of FruCOM instead of FruM (Ferri et al, 2008).…”

“…In principle, the neurons with intersexual structures are not produced; every neuron in the mAL cluster is either a perfect female-type or male-type neuron under fru loss-of-function conditions (Ito et al, 2012). By contrast, manipulations of a fru downstream element or some fru -interacting partners result in malformation of one or more sexually dimorphic characteristics of mAL neurons (Goto et al, 2011; Ito et al, 2016; Chowdhury et al, 2017; Sato et al, 2019). These observations suggest that FruM proteins operate as two-directional switches between the female-type and male-type developmental pathways in mAL neurons, whereas the specification of each sex-specific neural structure is achieved by pathway-specific molecules downstream of FruM.…”