Identification and characterization of a Drosophila nuclear proteasome regulator. A homolog of human 11 S REGgamma (PA28gamma ).
We report the cloning and characterization of a Drosophila proteasome 11 S REGgamma (PA28) homolog. The 28-kDa protein shows 47% identity to the human REGgamma and strongly enhances the trypsin-like activities of both Drosophila and mammalian 20 S proteasomes. Surprisingly, the Drosophila REG was found to inhibit the proteasome's chymotrypsin-like activity against the fluorogenic peptide succinyl-LLVY-7-amino-4-methylcoumarin. Immunocytological analysis reveals that the Drosophila REG is localized to the nucleus but is distributed throughout the cell when nuclear envelope breakdown occurs during mitosis. Through site-directed mutagenesis studies, we have identified a functional nuclear localization signal present in the homolog-specific insert region. The Drosophila PA28 NLS is similar to the oncogene c-Myc nuclear localization motif. Comparison between uninduced and innate immune induced Drosophila cells suggests that the REGgamma proteasome activator has a role independent of the invertebrate immune system. Our results support the idea that gamma class proteasome activators have an ancient conserved function within metazoans and were present prior to the emergence of the alpha and beta REG classes.
Masson
P
P
Department of Molecular Biology, Stockholm University, S-10691 Stockholm, Sweden.
Andersson
O
O
Petersen
U M
UM
Young
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism*; D004789:Enzyme Activation; D019143:Evolution, Molecular; D006801:Humans; D007150:Immunohistochemistry; D007448:Invertebrates; D007700:Kinetics; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism; D009124:Muscle Proteins; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D001324:Autoantigens; C099558:Ki antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D009687:Nuclear Proteins; C085047:PSME1 protein, human; D011506:Proteins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex