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The yeast rRNA biosynthesis factor Ebp2p is also required for efficient nuclear division
Costin N Ionescu1, Sofia Origanti, Michael A McAlear
1Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459-0175, USA.
Yeast (Chichester, England)
|October 30, 2004
Summary
Yeast Ebp2 protein is essential for both rRNA production and chromosome segregation. New mutants reveal distinct roles, with C-terminal deletions impacting nuclear division and Mad2p monitoring. This highlights Ebp2
Area of Science:
- Molecular genetics
- Cell biology
- Biochemistry
Background:
- The yeast Ebp2 protein is essential and localized to the nucleolus.
- It plays a role in the rRNA biosynthesis pathway, specifically in 27 SA precursor rRNA processing.
- Mutations affecting rRNA processing cluster in the conserved central region of Ebp2.
Purpose of the Study:
- To investigate the function of yeast Ebp2 protein beyond rRNA biosynthesis.
- To characterize the phenotypes of novel ebp2 mutants, particularly those affecting chromosome segregation.
- To determine the relationship between Ebp2's roles in rRNA processing and nuclear division.
Main Methods:
- Molecular genetic analysis of yeast Ebp2 protein.
- Creation and characterization of temperature-sensitive (ebp2-1) and truncation (ebp2 delta C50) mutants.
- Phenotypic analysis including growth rates, nuclear positioning, and chromosome segregation.
- Genetic complementation tests between different ebp2 alleles.
- Cytological analysis and Fluorescence-Activated Cell Sorting (FACS) analysis.
- Investigation of interactions with mitotic checkpoint proteins like Mad2p.
Main Results:
- Ebp2 protein is essential for both rRNA biosynthesis and chromosome segregation in yeast.
- The ebp2-1 mutant shows defects in 27 SA precursor rRNA processing.
- The ebp2 delta C50 mutant exhibits slow growth, nuclear division defects, and abnormal nuclear positioning.
- The nuclear division defects in ebp2 delta C50 are distinct from the rRNA processing defects in ebp2-1.
- Mad2p, a mitotic checkpoint protein, monitors the chromosome segregation activities of Ebp2p.
- The ebp2-1 and ebp2 delta C50 alleles genetically complement each other, indicating distinct functions.
Conclusions:
- Yeast Ebp2 protein has dual essential functions in rRNA biosynthesis and nuclear division.
- The C-terminal region of Ebp2 is critical for its role in chromosome segregation.
- Ebp2's involvement in chromosome segregation is regulated by the Mad2p-dependent mitotic checkpoint.
- These findings align with evidence suggesting human EBP2 also plays a role in chromosome segregation.