SPT7 encodes a subunit of SAGA, a multi-subunit coactivator complex that regulates transcription of some RNA polymerase II-dependent genes (2). A C-terminally truncated form of Spt7p is also found in an altered SAGA complex, termed SLIK (4) or SALSA (3), which lacks Spt8p and full-length Spt7p. Mutant analysis indicates that the C-terminal region of Spt7p is required for assembly of Spt8p into SAGA. In addition, Spt7p is required for normal amounts of two other SAGA components required for SAGA integrity, Spt20p and Ada1p, suggesting that Spt7p plays a critical role in SAGA complex formation (5, 6).

SPT7 was originally identified in a genetic screen for mutations that suppress Ty or solo Delta element insertions in the HIS4 or LYS2 promoters (1, 7). spt7 null mutant phenotypes include: slow growth, inositol auxotrophy, altered cell morphologies relative to wild-type cells, defects in sporulation, and defects in transcription of Ty elements (8). Many of the null mutant phenotypes are complemented by expression of the carboxy-terminal 459 amino acids of SPT7 (1332 amino acids long). Interestingly, the 414 amino acid human protein STAF65gamma, which is a component of the SAGA-related STAGA complex, is homologous to the carboxy-terminal 543 amino acids of Spt7p (9).

Characterized subunits of the SAGA complex include: Hfi1p, Ada2p, Ngg1p, Spt20p, Gcn5p, Spt3p, Spt7p, Spt8p, Tra1p, Taf5p, Taf6p, Taf9p, Taf10p, and Taf12p, Ubp8p, and Sgf11p (10, 11; reviewed in 3)

Last updated: 2006-07-03