Plays a pivotal role in regulating the expression of other pair-rule genes such as eve, ftz, and h. Plays a role in the developmental pathways of sex determination and neurogenesis (By similarity). Heterodimer runt and brother (or big brother) proteins. Expressed in a series of equally spaced stripes covering the trunk anlagen in the blastoderm embryo. By late blastoderm, expressed in the head lobes. The runt domain is responsible for the DNA-binding properties of the alpha subunit and also mediates interaction with subunit beta. The transactivation domain is located downstream of the runt domain.