tailieunhanh - Báo cáo khoa học: Consequences of COP9 signalosome and 26S proteasome interaction

The COP9 signalosome (CSN) occurs in all eukaryotic cells. It is a regula-tory particle of the ubiquitin (Ub)⁄26S proteasome system. The eight sub-units of the CSN possess sequence homologies with the polypeptides of the 26S proteasome lid complex and just like the lid, the CSN consists of six subunits with PCI (proteasome, COP9 signalosome, initiation factor 3) domains and two components with MPN (Mpr-Pad1-N-terminal) domains. | ềFEBS Journal Consequences of COP9 signalosome and 26S proteasome interaction Xiaohua Huang1 Bettina K. J. Hetfeld1 Ulrike Seifert2 Thilo Kahne3 Peter-Michael Kloetzel2 Michael Naumann3 Dawadschargal Bech-Otschir4 and Wolfgang Dubiel1 1 Division of Molecular Biology Department of Surgery Charite Universitatsmedizin Berlin Germany 2 Institute of Biochemistry Charites Universitatsmedizin Berlin Germany 3 Institut fur Experimentelle Innere Medizin Universitat Magdeburg Germany 4 MRC Human Genetics Unit Western General Hospital Edinburgh UK Keywords COP9 signalosome lid p53 PCI domain 26S proteasome Correspondence Division of Molecular Biology Department of Surgery Charite Universitatsmedizin Berlin Monbijoustr. 2 10117 Berlin Germany Fax 49 30 450522928 Tel 49 30 450522305 e-mail Received 9 May 2005 accepted 6 June 2005 doi The COP9 signalosome CSN occurs in all eukaryotic cells. It is a regulatory particle of the ubiquitin Ub 26S proteasome system. The eight subunits of the CSN possess sequence homologies with the polypeptides of the 26S proteasome lid complex and just like the lid the CSN consists of six subunits with PCI proteasome COP9 signalosome initiation factor 3 domains and two components with MPN Mpr-Pad1-N-terminal domains. Here we show that the CSN directly interacts with the 26S proteasome and competes with the lid which has consequences for the peptidase activity of the 26S proteasome in vitro. Flag-CSN2 was permanently expressed in mouse B8 fibroblasts and Flag pull-down experiments revealed the formation of an intact Flag-CSN complex which is associated with the 26S proteasome. In addition the Flag pull-downs also precipitated cullins indicating the existence of super-complexes consisting of the CSN the 26S pro-teasome and cullin-based Ub ligases. Permanent expression of a chimerical subunit Flag-CSN2-Rpn6 consisting of the N-terminal 343 amino acids of CSN2 and of the PCI domain of S9 Rpn6 .