THE DROSOPHILA TEASHIRT HOMEOTIC PROTEIN IS A DNA-BINDING PROTEIN ANDMODULO, A HOM-C REGULATED MODIFIER OF VARIEGATION, IS A LIKELY CANDIDATE FOR BEING A DIRECT TARGET GENE

The Drosophila teashirt (tsh) gene has an homeotic function which, in combination with HOM-C genes, determines thoracic and abdominal (trunk ) identities. Analysis of TSH protein distribution during embryogenesi s using a specific polyclonal antibody shows that it is nuclear. The p rotein is present with regional modulation in several tissues within t he trunk, suggesting additional tsh functions to those already studied . We identified a candidate tsh target shared with some HOM-C genes, t he modifier of variegation gene module (mod). The TSH zinc-finger prot ein recognizes in vitro two specific sites within a 5' control element of the mod gene which responds in vivo to tsh activity. TSH is theref ore a DNA binding protein and might directly control mod expression.