Rme1, which controls CLN2 expression in Saccharomyces cerevisiae, is a nuclear protein that is cell cycle regulated

Area of Science:

• Molecular Biology
• Cell Cycle Regulation
• Yeast Genetics

Background:

• Cell division commitment in Saccharomyces cerevisiae, known as Start, is regulated by cyclin-dependent kinase Cdc28 and G1 cyclins.
• Transcription factors SBF and MBF induce G1 cyclin transcription, but other regulators are suggested.
• Rme1, a known repressor of meiosis, was previously identified as an activator of CLN2 transcription.

Purpose of the Study:

• To elucidate the mechanism by which Rme1 activates CLN2 transcription.
• To analyze the cell cycle regulation of RME1 transcription and Rme1 protein localization.
• To confirm the role of Rme1 in cell cycle regulation beyond its known function in meiosis.

Main Methods:

• Analysis of Rme1 binding to specific Rme1 response elements in the CLN2 promoter.
• Detailed analysis of RME1 transcription timing during late mitosis and G1.
• Investigation of the roles of transcription factors Ace2 and Swi5 in RME1 expression.
• Monitoring of Rme1 protein levels and nuclear localization throughout the cell cycle.
• Observation of RME1 expression patterns in diploid cells lacking IME1 repressor function.

Main Results:

• Rme1 activates CLN2 gene expression by binding to two specific Rme1 response elements in the CLN2 promoter.
• RME1 transcription occurs at the end of mitosis and in G1, mediated by Ace2 and Swi5.
• Rme1 protein levels peak in G1, and the protein localizes to the nucleus during this phase.
• Periodic RME1 expression was observed in diploid cells, highlighting its role in CLN2 regulation.

Conclusions:

• Rme1 is a key activator of CLN2 transcription, directly influencing G1 cyclin expression.
• The cell cycle-regulated expression and nuclear localization of Rme1 are critical for its function in promoting cell division.
• Rme1 plays a significant role in regulating the G1 phase of the cell cycle in Saccharomyces cerevisiae.