SALSA, a variant of yeast SAGA, contains truncated Spt7, which correlates with activated transcription.
Spt-Ada-Gcn5 acetyltransferase (SAGA) is a previously described histone acetyltransferase/transcriptional coactivator complex in yeast. At promoters of certain genes (HIS3 and TRP3), SAGA has an inhibitory function involving a nonproductive TATA-binding protein interaction mediated by the Spt3 and Spt8 subunits. Related to this, Spt8-less SAGA is a major form of the complex under activating conditions for these genes. In the present study, we purify this activation-specific complex, called SALSA (SAGA altered, Spt8 absent). Besides lacking Spt8, SALSA contains Spt7 subunit that is truncated. Examining the role of this subunit, we find that C-terminally truncated SPT7 resulted in derepressed HIS3 transcription. Furthermore, when grown in rich media (repressing conditions), wild-type cells yielded predominantly SAGA, but Spt7 C-terminal truncations resulted primarily in a form of complex similar to SALSA. Thus, SALSA-like structure and activating function can be partially recapitulated in yeast by truncating the C terminus of Spt7. Overall, these results lead to a model that for a subset of promoters SAGA is inhibitory through Spt3, Spt8, and an Spt8-interacting subdomain of Spt7, whereas SALSA is a form of complex for positive transcriptional regulation. These data clarify a mechanism by which a transcriptional regulatory complex can switch between positive and negative modulation.
Sterner
David E
DE
The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.
Belotserkovskaya
Rimma
R
Berger
Shelley L
SL
D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D005656:Fungal Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010957:Plasmids; D011233:Precipitin Tests; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic
D005656:Fungal Proteins; C093107:SPT7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors