. "The Abdominal-B gene is a homeotic gene located in the distal-most region of the bithorax complex (BX-C). Based on complementation analysis it has been proposed that the gene contains two separable genetic elements, called the m and r elements. The r element has a chiefly regulatory function confined to parasegment 14. In a reverse Northern screen of the distal-most BX-C DNA, we found four distinct areas that are transcribed in the embryo. One of the transcripts spans a large genomic region which, upon disruption by rearrangement breakpoints, causes loss of r element function. This transcript is expressed in the early embryo in a single domain apparently corresponding to parasegment 14. We propose that the small homeoprotein encoded by the transcript acts as a trans-regulator to confer r element function." . . . "EMBO J." . "Wilcox M." . "Bienz M." . "Ali N." . "Henry C." . "Delorenzi M." . "Saari G." . "1988"^^ . "3223-3231" . "Evidence that the Abdominal-B r element function is conferred by a trans-regulatory homeoprotein." . "7" .