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Independent regulation of full-length and 5'-truncated PAS5 mRNAs in Saccharomyces cerevisiae
1Department of Biochemistry, University of Arizona, Tucson 85721, USA.
Abstract:
Peroxisome assembly in Saccharomyces cerevisiae requires the products of several genes. In this report, the PAS5 gene has been characterized. The gene is on the left arm of chromosome X and encodes a polypeptide with similarity to the mammalian peroxisome assembly factor-1 (PAF-1). Two different length transcripts are produced from the yeast PAS5 gene. The longer mRNAs encompass an open reading frame, while the shorter transcripts initiate 46-110 base pairs downstream of the first in-frame AUG. The longer transcripts are induced four-fold on medium containing fatty acids as the sole carbon source, while the shorter transcripts are induced up to ten-fold on medium containing glycerol as a carbon source. The full-length coding sequence encodes a protein with a calculated molecular weight of 30.7 kDa. A protein of 25 kDa could be translated from the shorter transcripts and would lack a very acidic domain found in the amino-terminal extension of the longer protein. The common portion of the proteins is very basic; the calculated pI of the longer polypeptide is 9.02 and that of the shorter protein is 10.06.
Insights
The yeast PAS5 gene is crucial for peroxisome assembly and produces two distinct protein variants with differing functions. These variants are regulated by specific carbon sources, highlighting their specialized roles in cellular processes.
Area of Science:
- Cell Biology
- Molecular Genetics
Background:
- Peroxisome biogenesis is a complex process in Saccharomyces cerevisiae, dependent on multiple genes.
- The PAS5 gene's role in peroxisome assembly has not been fully elucidated.
Purpose of the Study:
- To characterize the PAS5 gene in yeast.
- To investigate the structure and regulation of PAS5 gene products.
Main Methods:
- Gene mapping and transcript analysis.
- Analysis of protein coding sequences and physicochemical properties.
Main Results:
- PAS5 is located on chromosome X and its product shows similarity to mammalian PAF-1.
- Two transcripts of different lengths are generated, leading to two protein isoforms (30.7 kDa and 25 kDa).
- Transcript expression is differentially regulated by carbon sources: fatty acids induce longer transcripts, while glycerol induces shorter transcripts.
Conclusions:
- The PAS5 gene encodes at least two protein isoforms with distinct N-terminal domains.
- Differential expression suggests specialized functions for each PAS5 protein variant in yeast metabolism.
- The characterization of PAS5 provides insights into peroxisome assembly regulation.