A second nitrogen permease regulator in Saccharomyces cerevisiae

Area of Science:

• Molecular Biology
• Yeast Genetics
• Nutrient Transport

Background:

• Saccharomyces cerevisiae utilizes specific permeases for nutrient uptake, including urea and proline.
• Regulation of these permeases is crucial for yeast adaptation to varying nitrogen availability.
• Understanding the molecular mechanisms governing nitrogen permease expression is key to cellular metabolism studies.

Purpose of the Study:

• To characterize a Saccharomyces cerevisiae mutant with impaired urea and proline transport.
• To identify and analyze the function of a gene complementing this mutation.
• To elucidate the regulatory role of the identified protein in nitrogen permease expression.

Main Methods:

• Genetic complementation analysis of a yeast mutant.
• Gene cloning and protein characterization (PEST sequences, localization).
• mRNA expression analysis (Northern blotting) under different nitrogen conditions.

Main Results:

• A novel gene was identified, coding for a non-membrane-embedded protein with two PEST sequences.
• The corresponding mRNA is induced by urea and proline but not repressed by nitrogen catabolite repression.
• In the mutant, DUR3 mRNA (urea transporter) is upregulated, while PUT4 mRNA (proline transporter) is unaffected, suggesting specific post-transcriptional regulation.

Conclusions:

• The identified protein acts as a post-transcriptional regulator of nitrogen permeases in Saccharomyces cerevisiae.
• This regulatory mechanism specifically influences urea transport (DUR3) but not proline transport (PUT4).
• The findings provide new insights into the complex control of nutrient assimilation in yeast.