The hPLIC Proteins May Provide a Link between the Ubiquitination Machinery and the Proteasome

• Published in: Molecular cell Vol. 6; no. 2; pp. 409 - 419
• Main Authors: Kleijnen, Maurits F., Shih, Alan H., Zhou, Pengbo, Kumar, Sushant, Soccio, Raymond E., Kedersha, Nancy L., Gill, Grace, Howley, Peter M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2000
• Subjects: Amino Acid Sequence; Animals; Carrier Proteins; Cell Cycle Proteins; Cells, Cultured; Cysteine Endopeptidases - metabolism; Fungal Proteins - chemistry; Fungal Proteins - metabolism; Gene Expression Regulation - drug effects; Humans; Keratinocytes - cytology; Keratinocytes - metabolism; Male; Mice; Molecular Sequence Data; Multienzyme Complexes - metabolism; Proteasome Endopeptidase Complex; Recombinant Proteins - metabolism; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; Sequence Alignment; Sequence Homology, Amino Acid; Skin - cytology; Transfection; Tumor Necrosis Factor-alpha - pharmacology; Ubiquitins - chemistry; Ubiquitins - genetics; Ubiquitins - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/S1097-2765(00)00040-X

Although there is a binding site on the proteasome for the polyubiquitin chains attached to degradation substrates by the ubiquitination machinery, it is currently unclear whether in vivo the activities of the ubiquitination machinery and the proteasome are coupled. Here we show that two human homologs of the yeast ubiquitin-like Dsk2 protein, hPLIC-1 and hPLIC-2, physically associate with both proteasomes and ubiquitin ligases in large complexes. Overexpression of hPLIC proteins interferes with the in vivo degradation of two unrelated ubiquitin-dependent proteasome substrates, p53 and IκBα, but not a ubiquitin-independent substrate. Our findings raise the possibility that the hPLIC proteins, and possibly related ubiquitin-like family members, may functionally link the ubiquitination machinery to the proteasome to affect in vivo protein degradation.