The SUA7 gene that encodes the general transcription factor TFIIB is involved in selection of transcription start site. The sua7-3 allele resulted from R78C downshifts transcription initiation site and confers the cold-sensitive phenotype at 16℃(Csm-). We generated revertants of sua7-3 mutant at 16℃ by UV mutagenesis and identified the stb (suppressor of TFIIB) genes as suppressor of sua7-3. Genetic analysis revealed that there are three different recessive genes designated stb1, stb2, and stb3. The stb1-1 suppressor confers the temperature sensitive phenotype at 37℃. The STB1 wildtype gene was cloned using a YCp50 yeast genomic library and delimited within 2.8 kb DNA fragment. The stb genes are different from the ssu71, ssu72 and ssu73 genes isolated as suppressors of sua7-1(E62K). The SUA8(RPB1) gene which encodes the largest subunit of RNA polymerase II was isolated as a multicopy suppressor sua7-3. We are currently characterizing the cloned STB1 and isolating more revertants of sua7-3.