UGA4 and YBR062C Regulate Oxidative Stress Tolerance Under Heavy Metal Toxicity

Area of Science:

• Cellular stress response
• Gene regulation
• Metal toxicity

Background:

• Heavy metals induce cellular stress via oxidative damage and protein dysfunction.
• Ure2p, a glutathione S-transferase in Saccharomyces cerevisiae, confers resistance to metal-induced oxidative stress.
• Ure2p synthesis is regulated by a stress-responsive internal ribosome entry site (IRES) in the URE2 5' UTR.

Purpose of the Study:

• Investigate the mechanistic details of gene regulation in response to heavy metal stress.
• Identify novel contributors to heavy metal tolerance in Saccharomyces cerevisiae.
• Elucidate the role of UGA4 and YBR062C in metal resistance pathways.

Main Methods:

• Gene deletion and overexpression studies in Saccharomyces cerevisiae.
• Assessment of metal sensitivity using colony-forming unit assays.
• Genetic analysis, including double mutant construction.
• Analysis of URE2 mRNA and Ure2p protein levels under stress conditions.
• Polysome profiling to assess translational efficiency.
• Use of a URE2-IRES-dependent reporter assay.

Main Results:

• Deletion mutants of UGA4 and YBR062C exhibited significant sensitivity to cadmium, arsenite, and nickel.
• UGA4 and YBR062C function within the URE2 pathway, with double mutants showing no increased sensitivity compared to single ure2Δ mutants.
• Overexpression of URE2 rescued metal resistance in uga4Δ and ybr062cΔ mutants.
• UGA4 and YBR062C act post-transcriptionally, reducing Ure2p protein levels without affecting URE2 mRNA abundance.
• Reduced ribosomal association of URE2 mRNA and decreased IRES-dependent reporter activity were observed in the mutants.
• Cap-dependent translation and reporter mRNA levels remained unaffected.

Conclusions:

• UGA4 and YBR062C are novel contributors to heavy metal tolerance in Saccharomyces cerevisiae.
• These genes facilitate heavy metal resistance by enhancing the IRES-mediated translation of URE2 mRNA.
• The findings reveal a new regulatory mechanism for stress response genes involving IRES elements and accessory factors.