While screening for genes that affect the synthesis of yeast snRNPs, we Identified a thermosensitive mutant that abolishes the production of a reporter snRNA at the non-permissive temperature. This mutant defines a new gene, named BDF1. In a bdf1-1 strain, the reporter snRNA synthesized before the temperature shift remains stable at the non-permissive temperature. This demonstrates that the BDF1 gene affects the synthesis rather than the stability of the reporter snRNA and suggests that the BDF1 gene encodes a transcription factor. BDF1 Is present in single copy on yeast chromosome XII, and Is important for normal vegetative growth but not essential for cell viability. bdf1 null mutants share common phenotypes with several mutants affecting general transcription and are defective In snRNA production. BDF1 encodes a protein of 687 amino-acids containing two copies of the bromodomaln, a motif also present in other transcription factors as well as a new conserved domain, the ET domain, also present in Drosophlla and human proteins.