Thiamine Biosynthesis in Saccharomyces cerevisiae Is Regulated by the NAD⁺-Dependent Histone Deacetylase Hst1

Abstract

Genes encoding thiamine biosynthesis enzymes in microorganisms are tightly regulated such that low environmental thiamine concentrations activate transcription and high concentrations are repressive. We have determined that multiple thiamine (THI) genes in Saccharomyces cerevisiae are also regulated by the intracellular NAD ؉ concentration via the NAD ؉ -dependent histone deacetylase (HDAC) Hst1 and, to a lesser extent, Sir2. Both of these HDACs associate with a distal region of the affected THI gene promoters that does not overlap with a previously defined enhancer region bound by the thiamine-responsive Thi2/Thi3/Pdc2 transcriptional activators. The specificity of histone H3 and/or H4 deacetylation carried out by Hst1 and Sir2 at the distal promoter region depends on the THI gene being tested. Hst1/Sir2-mediated repression of the THI genes occurs at the level of basal expression, thus representing the first set of transcription factors shown to actively repress this gene class. Importantly, lowering the NAD ؉ concentration and inhibiting the Hst1/Sum1 HDAC complex elevated the intracellular thiamine concentration due to increased thiamine biosynthesis and transport, implicating NAD ؉ in the control of thiamine homeostasis.

Activation of Protein Kinase C-Mitogen-activated Protein Kinase Signaling in Response to Inositol Starvation Triggers Sir2p-dependent Telomeric Silencing in Yeast

“…5A). These observations are consistent with the model of coordinate regulation of genes in thiamine and NAD ϩ biosynthesis by the Hst1p sirtuin (50).…”

“…The Hst1p sirtuin, which was shown by Bedalov et al (35) to regulate BNA2 expression in response to NA, also regulates THI4 and other genes in thiamine biosynthesis in response to NA (50). To confirm that the pattern of BNA2 regulation we observed in response to inositol and temperature was also characteristic of Hst1p-regulated genes, we examined THI4 expression in wild type cells under these same growth conditions.…”

Reduced Ssy1-Ptr3-Ssy5 (SPS) Signaling Extends Replicative Life Span by Enhancing NAD+ Homeostasis in Saccharomyces cerevisiae

“…The IP sample was incubated overnight at 4°C with anti-HA monoclonal antibody (ab1424, Abcam) at a dilution of 1:150. Both IP and no-Ab samples were incubated with 60 l of ChIPgrade protein G beads (Cell Signaling Technology) for 2 h at 4°C and then washed as described (31). DNA was then eluted from the beads 2 times with 125 l of elution buffer (5ϫ Tris-EDTA plus 1% SDS).…”

The Nuts and Bolts of Transcriptionally Silent Chromatin in Saccharomyces cerevisiae

“…How a point mutation in a seemingly-unrelated protein could bypass the entire silencing apparatus at HM loci has been a source of fascination to scientists in the field. It is now understood that Sum1 forms a complex with Hst1 and Rfm1 that normally represses the promoters of genes involved in sporulation, de novo NAD + biosynthesis, and thiamine biosynthesis (Xie et al 1999;Bedalov et al 2003;Li et al 2010). Remarkably, the Sum1-1 protein gains the ability to self-associate and interact with ORC while reducing an affinity for direct DNA binding (Safi et al 2008).…”