HSP90 controls SIR2 mediated gene silencing.

Area of Science:

• Molecular Biology
• Yeast Genetics
• Cellular homeostasis

Background:

• Heat shock protein 90 (Hsp90) chaperone system is known to interact with telomeric proteins, influencing telomere structure dynamics.
• The precise mechanisms by which Hsp90 affects telomeric protein activity, particularly Sir2p, remain largely unexplored.

Purpose of the Study:

• To investigate the role of Hsp90 (specifically Hsp82 in yeast) in modulating the activity and abundance of the telomeric protein Sir2p.
• To elucidate the impact of Hsp90 homeostasis on telomere and mating type silencing in Saccharomyces cerevisiae.

Main Methods:

• Utilized a temperature-sensitive Hsp90-deficient yeast strain (iG170Dhsp82) to assess Sir2p levels and silencing.
• Investigated the effects of Hsp90 overexpression (via heat shock or plasmid) on Sir2p abundance and silencing.
• Examined the role of the co-chaperone Sba1 in Hsp90-mediated regulation of Sir2p.

Main Results:

• Hsp90 deficiency in yeast leads to reduced Sir2p levels, resulting in de-repression of telomere silencing and loss of mating type silencing.
• Overexpression of Hsp90 also causes a decrease in Sir2p levels, leading to impaired telomere silencing.
• The observed regulation of Sir2p by Hsp90 is independent of the co-chaperone Sba1.

Conclusions:

• Hsp90 homeostasis is critical for maintaining the cellular pool of Sir2p, thereby controlling the reversible nature of telomere silencing.
• This study reveals a novel regulatory pathway where Hsp90 influences Sir2p function, impacting essential cellular processes like silencing.
• The findings highlight the intricate relationship between molecular chaperones and telomere maintenance machinery.