Originally published as Genetics Published Articles Ahead of Print on April 15, 2007.

Genetics, Vol. 176, 801-813, June 2007, Copyright © 2007
doi:10.1534/genetics.106.068056

Characterization of BEAF Mutations Isolated by Homologous Recombination in Drosophila

Swarnava Roy, Matthew K. Gilbert and Craig M. Hart1

Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803

1 Corresponding author: Department of Biological Sciences, 202 Life Sciences Bldg., Louisiana State University, Baton Rouge, LA 70803.
E-mail: chart4{at}lsu.edu

The Drosophila BEAF-32A and BEAF-32B proteins bind to the scs' insulator and to hundreds of other sites on Drosophila chromosomes. These two proteins are encoded by the same gene. We used ends-in homologous recombination to generate the null BEAFAB-KO allele and also isolated the BEAFA-KO allele that eliminates production of only the BEAF-32A protein. We find that the BEAF proteins together are essential, but BEAF-32B alone is sufficient to obtain viable flies. Our results show that BEAF is important for both oogenesis and development. Maternal or zygotic BEAF is sufficient to obtain adults, although having only maternal BEAF impairs female fertility. In the absence of all BEAF, a few fertile but sickly males are obtained. Using both a chromosomal position-effect assay and an enhancer-blocking assay, we find that BEAF is necessary for scs' insulator function. Lack of BEAF causes a disruption of male X polytene chromosome morphology. However, we did not find evidence that dosage compensation was affected. Position-effect variegation of the wm4h allele and different variegating y transgenes was enhanced by the knockout mutation. Combined with the effects on male X polytene chromosomes, we conclude that BEAF function affects chromatin structure or dynamics.