The zeste locus of Drosophila melanogaster encodes a DNA-binding protein that 
can influence transcription. A number of sites recognized by this protein fall 
within genes associated with transvection, a phenomenon suggesting a form of 
gene regulation that is responsive to the proximity of a gene to its homologous 
allele on another chromosome. These recent observations continue a history of 
studies concerning zeste and transvection which has inspired molecular models 
linking chromosome structure and positioning to the modulation of gene 
expression.