Distribution and Molecular Characterization of mRNA-Binding Proteins Specific to the (U)15Region of 3′ UTR of the Mouse Catalase (Cas-1)

Abstract

The 3' UTR of the mouse Cas-1 mRNA, encoding the antioxidant enzyme catalase, has a U-rich motif that is conserved across species. This motif is an active site for complex and dynamic interactions involving RNA-binding proteins. The spatial, temporal, and phylogenetic distribution of the Cas-1 3'-UTR U-rich motif-specific RNA-binding proteins was evaluated by gel mobility shift and UV cross-linking assays. The specific RNA-protein complexes were observed in mouse tissue homogenates representing developmental stages as early as day 10 pc and ranged in molecular weight from approximately 38 kDa to approximately 52 kDa. These mRNA-protein complexes appeared in all vertebrate species examined (human, mouse, rat, dog, rabbit, chicken, fish, and frog) but not in insects. The approximately 38-kDa protein was the most prominent protein in vertebrates. The cDNA sequence of the mouse approximately 38-kDa protein was obtained by purification of the protein, microsequencing, and RT-PCR. The resulting 456-nt sequence, representing the partial internal cDNA sequence, and its deduced amino acid sequence were similar to the RNA recognition motif (RRM) of a protein superfamily, implicated in splicing, stability, localization, and translation of RNAs. Although the results suggest that cis element-binding activity could be a cytoplasmic regulator of Cas-1 mRNA metabolism, the significance of this binding remains to be determined.