High impact information on SPT8

• Positive and negative functions of the SAGA complex mediated through interaction of Spt8 with TBP and the N-terminal domain of TFIIA [1].
• Site-specific photocross-linkers and tethered protein cleavage reagents positioned on the NTD of TFIIA and assembled in PICs identified the SAGA subunit Spt8 and the TFIID subunit Taf4 as located near this surface [1].
• Two components of the RNA polymerase II machinery, Med13 (Srb9) and Spt8, were isolated as two-hybrid partners of the conserved TFIIS N-terminal domain [2].
• It is proposed that TFIIS and the Spt8-containing form of SAGA co-operate to rescue RNA polymerase II from unproductive elongation complexes, and that the Cdk8 module temporarily blocks transcription during transcript cleavage [2].
• Besides lacking Spt8, SALSA contains Spt7 subunit that is truncated [3].

Biological context of SPT8

• In addition, the predicted SPT8 amino acid sequence contains one copy of a sequence motif found in multiple copies in a number of other eukaryotic proteins, including the beta subunit of heterotrimeric G proteins [4].
• Mutations in SPT8 confer phenotypes similar to those caused by particular mutations in SPT15, which encodes the TATA-binding protein (TBP) [4].
• In an spt8 strain, where full-length Ty1 transcription and, therefore, transposition are reduced, most deletions were due to gene conversion of a 7-kb chromosomal interval flanked by a Ty1 element and a tRNA(Gly) gene [5].

Physical interactions of SPT8

• Conditions that induce HIS3 and TRP3 transcription result in an altered balance between these complexes strongly in favor of the form without Spt8 [6].
• We further find that Spt8 and SAGA compete with DNA to bind TBP rather than forming a triple complex [7].

Regulatory relationships of SPT8

• This genetic analysis has shown that an spt8 deletion mutation is suppressed by particular spt3 alleles [4].

Other interactions of SPT8

• The Saccharomyces cerevisiae SPT8 gene encodes a very acidic protein that is functionally related to SPT3 and TATA-binding protein [4].
• Our selection and screen has identified two additional genes, SPT7 and SPT8, that are also required for transcription initiation in delta sequences [8].

References