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Oligomerization activity of a double-stranded RNA-binding domain
Edward G Hitti1, Nina B Sallacz, Vera K Schoft
1Max F. Perutz Laboratories, Department of Cell Biology and Genetics, Institute of Botany, University of Vienna, Rennweg 14, 1030 Vienna, Austria.
FEBS Letters
|September 11, 2004
Summary
Xenopus laevis RNA-binding protein A (Xlrbpa) self-multimerizes via its third double-stranded RNA-binding domain (dsRBD). This dsRBD interaction is RNA-independent and crucial for activating protein kinase R (PKR).
Area of Science:
- Molecular Biology
- Protein Interactions
- RNA Biology
Background:
- Xenopus laevis RNA-binding protein A (Xlrbpa) is a conserved RNA-binding protein.
- It is associated with heterogeneous nuclear ribonucleoproteins (hnRNPs) and ribosomes.
- Xlrbpa contains three tandemly arranged double-stranded RNA-binding domains (dsRBDs).
Purpose of the Study:
- To identify the regions of Xlrbpa responsible for its self-interaction.
- To investigate the role of specific dsRBDs in protein multimerization.
- To explore the implications of Xlrbpa homomultimerization in biological pathways, such as PKR activation.
Main Methods:
- Yeast two-hybrid assays using Xlrbpa deletion constructs.
- Co-immunoprecipitation experiments with truncated Xlrbpa proteins.
- Expression of truncated proteins in yeast and Xenopus oocytes.
- Testing RNA-binding independence using RNases.
Main Results:
- Xlrbpa self-multimerizes, with the third dsRBD identified as the sole interacting domain.
- This homomultimerization activity is conserved in the human homologue, PACT.
- The third dsRBD's multimerization is independent of RNA binding.
- This domain is essential for the activation of the dsRNA-activated protein kinase PKR.
Conclusions:
- The third dsRBD of Xlrbpa exhibits homomultimerization activity.
- This RNA-independent dimerization is critical for PACT's role in PKR activation.
- The findings propose a model for PKR activation mediated by PACT multimerization.