With the goal of identifying factors that may regulate the binding specificity of the TATA-box binding protein (TBP), we have performed a genetic selection for suppressors of a TBP mutant that exhibits altered DNA-binding specificity in vivo and in vitro. The recognition of nonconsensus TATA sites by this TBP mutant leads to its ability to suppress the effects of promoter insertion mutations caused by the transposable element Ty (Spt- phenotype). A selection for suppressors of the Spt- phenotype of the TBP mutant has led to the identification of a novel gene, RTF1 (Restores TBP Function). The predicted RTF1 open reading frame encodes a 558 amino acid protein with a high content of charged amino acids and no significant homology to previously characterized proteins. RTF1 is not an essential gene; however, an rtf1 null allele causes an Spt- phenotype on its own and suppresses different TBP mutants in an allele-specific fashion, strongly arguing for a direct role of RTF1 in transcription. The original rtf1-1 mutation, which also confers allele-specific suppression on TBP mutants, encodes a single amino acid change in the highly charged amino-terminus of the protein. Using a functional, epitope-tagged version of the protein, RTF1 has been identified in yeast extracts by western analysis and has been found to be a nuclear protein by indirect immunofluorescence microscopy. Further characterization of RTF1 will be presented.