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Ribosomal association of poly(A)-binding protein in poly(A)-deficient Saccharomyces cerevisiae
1Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
Abstract:
Poly(A)-binding protein, the most abundant eukaryotic mRNP protein, is known primarily for its association with polyadenylate tails of mRNA. In the yeast, Saccharomyces cerevisiae, this protein (Pabp) was found to be essential for viability and has been implicated in models featuring roles in mRNA stability and as an enhancer of translation initiation. Although the mechanism of action is unknown, it is thought to require an activity to bind poly(A) tails and an additional capacity for an interaction with 60 S ribosomal subunits, perhaps via ribosomal protein L46 (Rpl46). We have found that a significant amount of Pabp in wild-type cells is not associated with polyribosome complexes. The remaining majority, which is found in these complexes, maintains its association even in yeast cells deficient in polyadenylated mRNA and/or Rpl46. These observations suggest that Pabp may not require interaction with poly(A) tails during translation. Further treatment of polyribosome lysates with agents known to differentially disrupt components of polyribosomes indicated that Pabp may require contact with some RNA component of the polyribosome, which could be either non-poly(A)-rich sequences of the translated mRNA or possibly a component of the ribosome. These findings suggest that Pabp may possess the ability to bind to ribosomes independently of its interaction with poly(A). We discuss these conclusions with respect to current models suggesting a multifunctional binding capacity of Pabp.
Insights
Poly(A)-binding protein (Pabp) is essential for yeast viability. Research suggests Pabp may bind ribosomes independently of mRNA poly(A) tails, indicating a multifunctional role in translation.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Protein-RNA Interactions
Background:
- Poly(A)-binding protein (Pabp) is a key eukaryotic mRNP protein associated with mRNA polyadenylate tails.
- In Saccharomyces cerevisiae, Pabp is essential for viability and linked to mRNA stability and translation initiation.
- Current models propose Pabp requires poly(A) tail binding and interaction with 60S ribosomal subunits (possibly via Rpl46).
Purpose of the Study:
- To investigate the role of Pabp-poly(A) tail interaction in translation.
- To determine if Pabp can associate with ribosomes independently of poly(A) tails.
- To explore Pabp's binding mechanisms within polyribosome complexes.
Main Methods:
- Analysis of Pabp localization in wild-type and mutant yeast cells (deficient in polyadenylated mRNA and/or Rpl46).
- Fractionation of polyribosome complexes.
- Treatment of polyribosome lysates with agents to disrupt ribosomal components.
Main Results:
- A significant portion of Pabp is not associated with polyribosome complexes in wild-type cells.
- Pabp remains associated with polyribosomes even in yeast lacking polyadenylated mRNA and/or Rpl46.
- Pabp dissociation studies suggest a requirement for interaction with RNA components of the polyribosome, not necessarily poly(A) tails.
Conclusions:
- Pabp may bind to ribosomes independently of poly(A) tails during translation.
- These findings challenge existing models and suggest a more complex, multifunctional binding capacity for Pabp.
- Pabp's interaction with ribosomes might involve other RNA elements within the polyribosome complex.