Spt8 Background Information The SPT8 gene encodes a 602 amino acid protein with an extremely acidic amino terminus (1). Spt8 is a component of the wild-type S. Cerevisiae SAGA complex which activates transcription of a subset of RNA-polymerase II-dependent genes (2). The interaction of TATA-binding protein (TBP) and SAGA at particular promoters and the functional interaction between Spt3 and TBP requires Spt8 (1,2). Wild-type SAGA inhibits TBP binding to the HIS3 promoter in vitro, while SAGA lacking Spt3 or Spt8 is not inhibitory (3,4). Therefore, the composition of SAGA may be dynamic in vivo and regulated through dissociable inhibitory subunits (3). Normal transcription of Ty elements, and initiation of Ty transcription from delta sequences involves Spt8 (5). Mutations in the SPT8 gene result in a sporulation defect and are strong suppressors of insertion mutations caused by Ty elements and long terminal repeat sequences called delta sequences (1,5,6).
