The association of the human PM/Scl-75 autoantigen with the exosome is dependent on a newly identified N terminus.
The exosome is a complex of 3' --> 5' exoribonucleases that functions in a variety of cellular processes, all concerning the processing or degradation of RNA. Paradoxically, the previously described cDNA for the human autoantigenic exosome subunit PM/Scl-75 (Alderuccio, F., Chan, E. K., and Tan, E. M. (1991) J. Exp. Med. 173, 941-952) encodes a polypeptide that failed to interact with the exosome complex. Here, we describe the cloning of a more complete cDNA for PM/Scl-75 encoding 84 additional amino acids at its N terminus. We show that only the longer polypeptide is able to associate with the exosome complex. This interaction is most likely mediated by protein-protein interactions with two other exosome subunits, hRrp46p and hRrp41p, one of which was confirmed in a mammalian two-hybrid system. In addition we show that the putative nuclear localization signal present in the C-terminal region of PM/Scl-75 is sufficient, although not essential for nuclear localization of the protein. Moreover, the deletion of this element abrogated the nucleolar accumulation of PM/Scl-75, although its association with the exosome was not disturbed. This suggests that this basic element of PM/Scl-75 plays a role in targeting the exosome to the nucleolus.
Raijmakers
Reinout
R
Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, University of Nijmegen, 6525 GA Nijmegen, The Netherlands.
Egberts
Wilma Vree
WV
van Venrooij
Walther J
WJ
Pruijn
Ger J M
GJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001324:Autoantigens / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D002277:Carcinoma; D002466:Cell Nucleolus / Q000737:chemistry; D018076:DNA, Complementary; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D017434:Protein Structure, Tertiary; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D001324:Autoantigens; D018076:DNA, Complementary; D009687:Nuclear Proteins; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C077044:EXOSC10 protein, human