Involvement of proteasomal subunits zeta and iota in RNA degradation

• Published in: Biochemical journal 1997-08, Vol.326 ( Pt 1) (1), p.93-98
• Main Authors: Petit, F, Jarrousse, A S, Dahlmann, B, Sobek, A, Hendil, K B, Buri, J, Briand, Y, Schmid, H P
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Cysteine Endopeptidases - isolation & purification; Cysteine Endopeptidases - metabolism; Hydrolysis; Liver - enzymology; Multienzyme Complexes - isolation & purification; Multienzyme Complexes - metabolism; Proteasome Endopeptidase Complex; Ribonucleases - metabolism; RNA, Viral - metabolism; Tobacco mosaic virus; Tobacco Mosaic Virus - genetics
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3260093

We have identified two distinct subunits of 20 S proteasomes that are associated with RNase activity. Proteasome subunits zeta and iota, eluted from two-dimensional Western blots, hydrolysed tobacco mosaic virus RNA, whereas none of the other subunits degraded this substrate under the same conditions. Additionally, proteasomes were dissociated by 6 M urea, and subunit zeta, containing the highest RNase activity, was isolated by anion-exchange chromatography and gel filtration. Purified subunit zeta migrated as a single spot on two-dimensional PAGE with a molecular mass of approx. 28 kDa. Addition of anti-(subunit zeta) antibodies led to the co-precipitation of this proteasome subunit and nuclease activity. This is the first evidence that proteasomal alpha-type subunits are associated with an enzymic activity, and our results provide further evidence that proteasomes may be involved in cellular RNA metabolism.