SPT20/ADA5 encodes a novel protein functionally related to the TATA-binding protein and important for transcription in Saccharomyces cerevisiae

Mutations selected as suppressors of Ty and solo delta insertion mutations in Saccharomyces cerevisiae have identified a number of genes important for transcription initiation. One of these genes, SPT15, encodes the TATA-binding protein, and three others, SPT3, SPT7, and SPT8, encode proteins functionally related to the TATA-binding protein. To identify additional related functions, we have selected for new spt mutations. This work has identified one new gene, SPT20. Null mutations in SPT20 cause poor growth and a set of severe transcriptional defects very similar to those caused by nun mutations in SPT3, SPT7, and SPT8 and also very similar to those caused by certain missense mutations in SPT15. Consistent with it having an important function in transcription in vivo, SPT20 was also recently identified as ADAS and has been shown to be important for transcriptional activation (G. A. Marcus, J. Horiuchi, N. Silverman, and L. Guarente, Mol. Cell. Biol. 16:3197-3205, 1996).