H3K4 methyltransferase Set1 is involved in maintenance of ergosterol homeostasis and resistance to Brefeldin A

Abstract

Set1 is a conserved histone H3 lysine 4 (H3K4) methyltransferase that exists as a multisubunit complex. Although H3K4 methylation is located on many actively transcribed genes, few studies have established a direct connection showing that loss of Set1 and H3K4 methylation results in a phenotype caused by disruption of gene expression. In this study, we determined that cells lacking Set1 or Set1 complex members that disrupt H3K4 methylation have a growth defect when grown in the presence of the antifungal drug Brefeldin A (BFA), indicating that H3K4 methylation is needed for BFA resistance. To determine the role of Set1 in BFA resistance, we discovered that Set1 is important for the expression of genes in the ergosterol biosynthetic pathway, including the rate-limiting enzyme HMG-CoA reductase. Consequently, deletion of SET1 leads to a reduction in HMG-CoA reductase protein and total cellular ergosterol. In addition, the lack of Set1 results in an increase in the expression of DAN1 and PDR11, two genes involved in ergosterol uptake. The increase in expression of uptake genes in set1Δ cells allows sterols such as cholesterol and ergosterol to be actively taken up under aerobic conditions. Interestingly, when grown in the presence of ergosterol set1Δ cells become resistant to BFA, indicating that proper ergosterol levels are needed for antifungal drug resistance. These data show that H3K4 methylation impacts gene expression and output of a biologically and medically relevant pathway and determines why cells lacking H3K4 methylation have antifungal drug sensitivity.chromatin | gene regulation | histone methylation | epigenetics M odifications on histones, such as phosphorylation, acetylation, methylation, and ubiquitination, have been implicated in gene expression and silencing (1, 2). One modification on histone H3 that is associated with active gene expression is the methylation of lysine 4 (H3K4) (3, 4). H3K4 methylation is present concurrently in mono-, di-, and trimethyl forms in the cell (1, 2). Primarily, H3K4 methylation is maintained in a pattern that has trimethylation enriched at the 5′ end of ORFs, dimethylation throughout the gene, and monomethylation enriched near the 3′ end (3, 4). In humans, H3K4 methylation is mediated by methyltransferases MLL1-4 and Set1A and -B complexes, which are homologous to the yeast Set1 H3K4 methyltransferase complex (5-12). In addition, Set1 and the human homologs are known to interact with the Ser5-phosphorylated C-terminal tail domain of RNA polymerase II (3). More recently, di-and trimethylated H3K4 have been shown to be docking sites for chromodomain and plant homeodomain (PHD) fingercontaining proteins (1,13,14). Taken together, this and other studies suggest that the methylation of histone H3K4 plays a role in mediating gene expression by recruiting effector proteins.In Saccharomyces cerevisiae, the Set1 complex (Set1C or COMPASS) is responsible for the methylation of histone H3K4 and the kinetochore protein Dam1 (5,[15][16][17][18][19]. Loss of the catalytic protei...

Htz1 and Set1 Regulate Ergosterol Levels in Response to Environmental Stress

“…Hence, low levels of ergosterol might activate the stressresponse genes in a Set1 and Htz1 dependent manner. This hypothesis is also supported by a recent work (South et al, 2013) that shows Set1 dependent methylation is involved in maintaining the ergosterol homeostasis. Direct measurement of ergosterol levels in these strains confirmed this observation ( Figure 5).…”

“…However, Set1 is a member of COMPASS complex (Krogan et al, 2002) and deletion of different subunits of COMPASS decreased carotenoid production ( Figure 1). Set1 was also recently shown to enhance ergosterol production through transcriptional regulation of multiple genes in the mevalonate pathway (South et al, 2013). Together, these data suggest that H3K4me 3 is an important epigenetic mark that effects ergosterol production as well as production of other isoprenoids.…”

Coordination of Cell Cycle Progression and Mitotic Spindle Assembly Involves Histone H3 Lysine 4 Methylation by Set1/COMPASS

“…Possibly, this is due to the more frequent analyses of steady-state conditions, for which H3K4 methylation appears to have a rather limited impact on mRNA levels, compared to dynamic gene expression processes, which appear to be impacted more strongly (Margaritis et al 2012;Weiner et al 2012). A notable exception is the Set1-dependent expression of genes required for ergosterol synthesis, which provides cells with resistance to the antifungal compound Brefeldin A (South et al 2013).…”

Bile Acid Sodium Symporter BASS6 Can Transport Glycolate and Is Involved in Photorespiratory Metabolism in Arabidopsis thaliana

“…The PCR product was cloned into the pRS415-ADH1 vector (ATCC) using BamHI and XhoI restriction sites. Yeast transformations were performed as previously described with BY4741 mat a wild-type and ady2D strains (GE Dharmacon) (South et al, 2010(South et al, , 2013.…”