The GIS2 Gene Is Repressed by a Zinc-Regulated Bicistronic RNA in Saccharomyces cerevisiae

Abstract

Zinc homeostasis is essential for all organisms. The Zap1 transcriptional activator regulates these processes in the yeast Saccharomyces cerevisiae. During zinc deficiency, Zap1 increases expression of zinc transporters and proteins involved in adapting to the stress of zinc deficiency. Transcriptional activation by Zap1 can also repress expression of some genes, e.g., RTC4. In zinc-replete cells, RTC4 mRNA is produced with a short transcript leader that is efficiently translated. During deficiency, Zap1-dependent expression of an RNA with a longer transcript leader represses the RTC4 promoter. This long leader transcript (LLT) is not translated due to the presence of small open reading frames upstream of the RTC4 coding region. In this study, we show that the RTC4 LLT RNA also plays a second function, i.e., repression of the adjacent GIS2 gene. In generating the LLT transcript, RNA polymerase II transcribes RTC4 through the GIS2 promoter. Production of the LLT RNA correlates with the decreased expression of GIS2 mRNA and mutations that prevent synthesis of the LLT RNA or terminate it before the GIS2 promoter renders GIS2 mRNA expression and Gis2 protein accumulation constitutive. Thus, we have discovered an unusual regulatory mechanism that uses a bicistronic RNA to control two genes simultaneously.

Characterization of Bicistronic Transcription in Budding Yeast

“…RTC4_GIS2 is another case where bicistronic transcription regulates translation of monocistronic transcripts, although no clear mechanism is known for this phenomenon. In contrast, the bicistronic transcript RTC4_GIS2 can repress translation of both monocistronic transcripts ( 22 ).…”

Transcriptome Analysis and Expression Profiling of Molecular Responses to Cd Toxicity in Morchella spongiola

“…2 up-regulated ZRT gene (F751_0752 and F751_4157) were predicted resist Cd stress at the early growth stage of microalgae [19]. The levels of the ZRT1, ZRT3, and FET4 metal transporters of Saccharomyces cerevisiae are increased during zinc deficiency by Zap1 to facilitate zinc uptake and mobilize zinc stored in the vacuole [39]. In our study, 3 ZRT genes were up-regulated under 0.15 mg/L treatment, suggesting that low concentrations of Cd might lead to competitive zinc deficiency, then induces expression of zinc-regulated transporter genes, which helped to maintain intracellular zinc homeostasis.…”

Changes in transcription start sites of Zap1‐regulated genes during zinc deficiency: Implications for HNT1 gene regulation

“…Zap1 binds to one or more conserved 11 bp sequences in its target promoters that has the consensus sequence of ACCTTNAAGGT (where N is any base) called a zinc-responsive element (ZRE). Previous studies have led to the identification of over 80 genes in the S. cerevisiae genome that are likely to be direct targets of Zap1 regulation (Bird, Gordon, Eide, & Winge, 2006;Lyons et al, 2000;MacDiarmid, Taggart, Jeong, Kerdsomboon, & Eide, 2016;De Nicola et al, 2007;Singh, Yadav, & Rajasekharan, 2017;Taggart et al, 2018;Wu et al, 2008Wu et al, , 2009. For most Zap1-regulated genes studied to date, Zap1-mediated increases in RNA level result in increased levels of the encoded proteins (Eide, 2009).…”