title: Primary structures of two homologous subunits of PA28, a gamma-interferon-inducible protein activator of the 20S proteasome.
abstract: The primary structures of two proteins that comprise PA28, an activator of the 20S proteasome, have been determined by cDNA cloning and sequencing. These protein subunits, termed PA28 alpha and PA28 beta, are about 50% identical to one another and are highly conserved between rat and human. PA28 alpha and PA28 beta are homologous to a previously described protein, Ki antigen, whose function is unknown. PA28 alpha, but neither PA28 beta nor Ki antigen, contains a 'KEKE motif', which has been postulated to promote the binding of proteins having this structural feature. PA28 alpha and PA28 beta were coordinately regulated by gamma-interferon, which greatly induced mRNA levels of both proteins in cultured cells. The mRNA level of the Ki antigen also increased in response to gamma-interferon treatment, but the magnitude of the increase was less than that for the PA28s, and the effect was transient. These results demonstrate the existence of a new protein family, at least two of whose members are involved in proteasome activation. They also provide the basis for future structure/function studies of PA28 subunits and the determination of their relative physiological roles in the regulation of proteasome activity.
authors.affiliation: Institute for Enzyme Research, University of Tokushima, Japan.
authors.forename: J Y
authors.initials: JY
authors.lastname: Ahn
authors.forename: N
authors.initials: N
authors.lastname: Tanahashi
authors.forename: K
authors.initials: K
authors.lastname: Akiyama
authors.forename: H
authors.initials: H
authors.lastname: Hisamatsu
authors.forename: C
authors.initials: C
authors.lastname: Noda
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: C H
authors.initials: CH
authors.lastname: Chung
authors.forename: N
authors.initials: N
authors.lastname: Shibmara
authors.forename: P J
authors.initials: PJ
authors.lastname: Willy
authors.forename: J D
authors.initials: JD
authors.lastname: Mott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D019394:Ki-67 Antigen; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000378:metabolism*; D009124:Muscle Proteins; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D046988:Proteasome Endopeptidase Complex; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid
chemical_list: D018797:Cell Cycle Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D019394:Ki-67 Antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C085047:PSME1 protein, human; D011506:Proteins; C490050:Psme1 protein, rat; C490052:Psme2 protein, rat; D012333:RNA, Messenger; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; C486207:PSME2 protein, human; D046988:Proteasome Endopeptidase Complex