Distinct mRNA-Binding Proteins Interacting with Short Repeat Sequences of the 3′ UTR May Be Involved in the Post-Transcriptional Regulation of the Mouse Catalase Gene,Cas-1

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Abstract
The 3′ untranslated region (UTR) of the mouse catalase gene (Cas-1) is demonstrated to be an active site for specific protein interactions. We have identified two regions of the Cas-1 3′ UTR mRNA that bind to distinct cytoplasmic proteins: one containing a (CA)31 repeat with UA octomer (RNA 5) and another with a (U)15 tract (RNA 6). RNA 5 interacts with one set of protein complexes (a, b, and c) whereas RNA 6 interacts with another (x, y, and z) in a sequence-specific manner. These RNA–protein complexes are development-, tissue-, and genotype-specific. The proteins involved in the two sets of complexes are different. Further characterization of the proteins involved in these interactions has revealed the presence of a single protein of ∼70 kD that binds RNA 5, and two proteins ∼38 kD and ∼47 kD that bind to RNA 6. The ∼70-kD and ∼38-kD proteins are also associated with the polysomal fractions and may play a role in the post-transcriptional regulation of Cas-1. Although the observed 3′ UTR RNA–protein interactions are hypothesized to be important in post-transcriptional regulation of this gene in rodents, specific RNA sequences and their associated proteins identified in this report would now permit the elucidation of the mechanisms of their action at the molecular level.