Abstract
In Saccharomyces cerevisiae, class II gene promoters contain two classes of TATA elements: the TATA box and the TATA-like element. Functional loss of TFIID and SAGA transcription complexes selectively impacts steady-state mRNA levels expressed from TATA-like element-containing (i.e., TATA-less) and TATA box-containing promoters, respectively. While nascent RNA analysis has revealed that TFIID and SAGA are required for both types of promoters, the division of their roles remains unclear. We show here that transcription from the PGK1 promoter decreased in some cases by more than half after disruption of the TATA box or SPT3 (spt3Δ), whereas spt3Δ did not affect transcription from the TATA-less promoter, consistent with the prevailing view that Spt3 functions specifically in a TATA box-dependent manner. Transcription from this promoter was abolished in the spt3Δ taf1-N568Δ strain but unaffected in the taf1-N568Δ strain, regardless of TATA box presence, suggesting that TFIID was functionally dispensable for PGK1 transcription at least in the SPT3 strain. Furthermore, transcription from the TATA box-containing PGK1 promoter was slightly reduced in the taf1 strain lacking TAND (taf1-ΔTAND) upon temperature shift from 25 to 37 ℃, with restoration to normal levels within 2 h, in an Spt3-dependent manner. Interestingly, when SPT3 was reintroduced into the spt3Δ TAF1, spt3Δ taf1-N568Δ or spt3Δ taf1-ΔTAND strain, TATA box-dependent transcription from this promoter was largely restored, but TFIID independence in transcription was not restored, especially from the TATA-less promoter, and transient TAND/Spt3-dependent fluctuations of transcription after the temperature shift were also not recapitulated. Collectively, these observations suggest that Spt3 has multiple functions in PGK1 transcription, some of which may be intimately connected to Taf1 function and may therefore become unrestorable when the TFIID and SAGA functions are simultaneously compromised.
Highlights
During eukaryotic transcription of class II genes, a set of general transcription factors (GTFs; TFIIA, B, D, E, F and H) assemble at the core promoter region alongside Mediator and RNA polymerase II (Pol II) to form a pre-initiation complex (PIC) that directs accurate transcriptional initiation (Thomas and Chiang, 2006; Hahn and Timmers, 2019; Fischer et al, 2019)
TFIID was detected at the PGK1 promoter at 25 °C (Venters et al, 2011), and occupancy increased after heat shock (Kuras et al, 2000), suggesting that TFIID might yet be involved in PGK1 transcription
During the preliminary stage of this work, we observed that the effects of taf1 mutations on PGK1 transcription differed between two distinct types of taf1 strain: those carrying SPT3 at the native locus and those with chromosomal spt3Δ complemented with plasmid-borne SPT3
Summary
During eukaryotic transcription of class II genes, a set of general transcription factors (GTFs; TFIIA, B, D, E, F and H) assemble at the core promoter region alongside Mediator and RNA polymerase II (Pol II) to form a pre-initiation complex (PIC) that directs accurate transcriptional initiation (Thomas and Chiang, 2006; Hahn and Timmers, 2019; Fischer et al, 2019). The core structural module contains five subunits that are identical (Taf and 12) and two that are homologous (Spt and Ada1) to subunits of TFIID, indicating that SAGA and TFIID are closely related transcription complexes (Helmlinger and Tora, 2017). SAGA may play a similar role to TFIID in delivering TBP to the core promoter via the function of the TBP-binding module comprising Spt and Spt, the former of which is homologous to the Taf11/13 heterodimer of TFIID (Birck et al, 1998; Bhaumik, 2011; Han et al, 2014; Helmlinger and Tora, 2017). Spt and Spt of SAGA bind to distinct surfaces of TBP, which are bound by Taf11/13 and TAND of TFIID, respectively (Anandapadamanaban et al, 2013; Han et al, 2014; Patel et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
