Primary structures of two homologous subunits of PA28, a γ-interferon-inducible protein activator of the 20S proteasome

Young Ahn Joon Young Ahn, Tanahashi Nobuyuki Tanahashi, Akiyama Kin-ya Akiyama, Hisamatsu Hiroshi Hisamatsu, Noda Chiseko Noda, Tanaka Keiji Tanaka, Ha Chung Chin Ha Chung, Shibmara Naoki Shibmara, Patricia J. Willy, Joni D. Mott, Clive A. Slaughter, George N. DeMartino

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180 Scopus citations


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 PA28α and PA28β, are about 50% identical to one another and are highly conserved between rat and human. PA28α and PA28β are homologous to a previously described protein, Ki antigen, whose function is unknown. PA28α, but neither PA28β nor Ki antigen, contains a 'KEKE motif', which has been postulated to promote the binding of proteins having this structural feature. PA28α and PA28β were coordinately regulated by γ-interferon, which greatly induced mRNA levels of both proteins in cultured cells. The mRNA level of the Ki antigen also increased in response to γ-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.

Original languageEnglish (US)
Pages (from-to)37-42
Number of pages6
JournalFEBS Letters
Issue number1
StatePublished - Jun 5 1995


  • Ki antigen
  • Multicatalytic proteinase complex
  • Proteasome
  • Proteasome activator PA28
  • cDNA cloning
  • γ-Interferon

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology


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