Genetic analysis of the nucleosome remodelling factor (NURF). P. Badenhorst , H. Xiao , R. Sandaltzopoulous , C. Wu. Laboratory of Molecular Cell Biology, National Cancer Institute, Bethesda, MD.

   The compaction of DNA in chromatin represents a formidable obstacle to transcription. Before an RNA polymerase complex can be assembled on a promoter, and a gene transcribed, this barrier must be alleviated by disruption or displacement of nucleosomes. The promoters of the small heat-shock genes have provided a useful model to explore how this is achieved in Drosophila. Numerous studies have revealed that chromatin assembled in vitro on the hsp70 and hsp26 promoters can be disrupted by the action of the GAGA transcription factor. Biochemical complementation defined a complex of four proteins, the nucleosome remodelling factor (NURF), which is required for GAGA-mediated chromatin disruption. The identities of three of the four subunits are known: the ISWI ATPase, a WD40 repeat protein p55 and the p38 pyrophosphatase. Here we report the identification of the large subunit of NURF, p301. We have isolated mutants in the large subunit of NURF and the p38 pyrophosphatase subunit. In combination with existing iswi mutants (Deuring et al., pers. comm.) we have begun to address the biological activities and targets of the NURF complex.