karyotes exert their effects over large distances. 
This laboratory has obtained electron microscopic 
and biochemical evidence for in vitro formation of 
a DNA loop mediated by Ubx protein binding to 
two sites near the Ubx transcription start site. For- 
mation of this loop may be aided by the presence of 
intrinsically curved sequences in the spacer DNA 
between the two sites. DNA constructs in which 
various combinations of the two binding sites and 
the spacer have been mutated or rearranged are 
being tested in vitro for effects on loop formation. 
Although there is some evidence for autoregula- 
tion, the potential role of this loop in vivo is more 
PUBLICATIONS 
difficult to assess, since normal Ubx expression in 
embryos requires extensive upstream sequences; 
this creates difficulty in handling. The behavior of 
these mutations is therefore being assessed in cul- 
tured cells, using a smaller and more manageable 
Ubx promoter fragment. The laboratory is particu- 
larly interested in the possibility that loop-based 
mechanisms may be involved in the regulation of 
downstream target genes. 
Dr. Beachy is also Assistant Professor of Molecu- 
lar Biology and Genetics at The Johns Hopkins Uni- 
versity School of Medicine. 
Articles 
Beachy, PA., Krasnow, M.A., Gavis, E.R., and Hogness, D.S. 1988. An Ultrabithorax protein binds sequences 
near its own and the Antennapedia PI promoters. Cell 55:1069-1081. 
Kornfeld, K., Saint, R.B., Beachy, PA. , Harte, P.J., Peattie, D.A., and Hogness, D.S. 1989. Structure and expres- 
sion of a family of Ultrabithorax mRNAs generated by alternative splicing and polyadenylation in Dro- 
sophila. Genes Dev 3:243-258. 
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