DmSNAPc domains for subunit assembly and DNA binding

Abstract

The small nuclear RNA activating protein complex (SNAPc) is the major unique transcription factor required for transcription of genes coding for small nuclear RNAs (snRNAs). In the fruit fly Drosophila melanogaster, DmSNAPc contains three distinct subunits (DmSNAP190, DmSNAP50, and DmSNAP43) that form a complex before binding to an snRNA gene promoter. We have used mutational analysis to identify domains within each subunit of DmSNAPc that are required for complex formation with the other two subunits in vivo. Also, we mapped domains in each subunit that are required for the DNA‐binding activity of DmSNAPc. We have found that the most evolutionarily conserved regions of the proteins are involved in SNAP complex assembly. Nevertheless, we found that domains outside of the conserved regions are also important for the DNA binding activity of DmSNAPc, even though they are not required for subunit assembly. Comparing our findings with published results in the human system indicates not only many important similarities but also significant differences in this ancient though rapidly evolving system. This work is supported by National Science Foundation grants MCB‐0131151 and MCB‐0641350 and in part by the California Metabolic Research Foundation. M. T. is a recipient of an Arne N. Wick Pre‐doctoral Research Fellowship from the California Metabolic Research Foundation.