An Interaction Map Of Chinese Liver 26S Proteasome Subunits

The 26S proteasome is a multi-subunit protein complex commonly available in most eukaryotic cells.It is responsible for the degradation of many cellular proteins, for example the cell cycle protein,oncogene product and MHC-â… restricting antigen. As a result,it plays a very important role in some cellular process,such as the regulation of cell cycle,cell apoptosis,antigen presentation,gene transcription and so on.The 26 S proteasome complex is composed of two subcomplexes,the 20 S catalytic particle and the 19 S regulatory particle.The 20 S particle has a cylinder-shaped structure containing four stacked heptameric rings that form the proteolytic chamber.The 20 S cylinder is capped on both sides by a 19 S particle to form the 26 S proteasome.The 19 S particle is composed of at least 17 proteins that form two subcomplexes;the "base" complex is composed of six AAA family of ATPases and three other proteins,and the "lid" complex is composed of eight non-ATPase proteins.It is generally believed that the 19 S particle plays two major roles in facilitating protein degradation by the 20 S particle.The first is to recognize and position ubiquitinated protein substrates,and the second is to unfold the protein substrates so that they can be inserted to the proteolytic chamber of the 20 S catalytic particle.How these events occur in the 19 S particle is unclear,and how the individual subunits participate in the regulatory functions also remains unknown.Human liver is a most important part of human tissue,it play the pivot role in human activities.The proteasome interaction maps of human liver are very important to analysis and cure the human liver disease.In this work,proteasome subunit ORFs were isolated from the liver tissues of Chinese people and constructed into the yeast two-hybrid plasmids.Then the yeast two-hybrid system was applied to detect the interactions between 26S proteasome subunits.We obtained 34 proteasome subunit ORFs.After screening 1156 subunit interactions,we obtained 112 positive interactions,about 10%of which were verified by in vito binding assay.We also transfected different subunits with the different fluoresce tag into the HeLa cells and observed the co-localization of interacting subunits.41%of our obtained 26S proteasome interactions have been reported previously.We also obtained many novel 26S proteasome interactions.Our results implied some mechanism of the formation of the 26S proteasome complex.