Study of the functional interaction between the Fab-7 and Fab-8 boundaries and the upstream promoter region in Drosophila Abd-B gene

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334 Russia

^* To whom correspondence should be addressed. Email: georgiev_p{at}mail.ru.

	Abstract

Boundary elements have been found in the regulatory region of the Drosophila Abd-B gene, which is subdivided into a series of iab domains. The best studied Fab-7 and Fab-8 boundaries flank the iab-7 enhancer and isolate it from the four promoters regulating Abd-B expression. Recently, binding sites for the Drosophila homolog of the vertebrate insulator protein CTCF have been identified in the Fab-8 boundary and upstream of the Abd-B promoter A, with no CTCF binding to the Fab-7 boundary being detected either in vivo or in vitro. Taking into account the inability of the yeast GAL4 activator to stimulate white promoter when its binding sites are separated by a 5 kb yellow gene, we have tested the functional interactions between the Fab-7 and Fab-8 boundaries and between these boundaries and the upstream promoter A region containing dCTCF binding site. It has been found that dCTCF binding sites are essential for pairing between two Fab-8 insulators. However, a strong functional interaction between the Fab-7 and Fab-8 boundaries suggest that additional, as yet unidentified proteins are involved in long-distance interactions between them. We have also shown that Fab-7 and Fab-8 boundaries effectively interact with the upstream region of the Abd-B promoter.