Exosome Component 3 (EXOSC3)

The deduced 275-amino acid RRP40 protein is 88% and 30% identical to the mouse and yeast sequences, respectively. Western blot analysis and immunofluorescence microscopy showed expression of a 31-kD protein in the nucleus, with additional forms expressed in the cytoplasm and the highest concentration in nucleolus.

Using a cell-free RNA decay system, Chen et al. (2001) demonstrated that the mammalian exosome is required for rapid degradation of ARE-containing RNAs but not for poly(A) shortening. They found that the mammalian exosome does not recognize ARE-containing RNAs on its own. ARE recognition required certain ARE-binding proteins that could interact with the exosome and recruit it to unstable RNAs, thereby promoting their rapid degradation.