The J domain of Tpr2 regulates its interaction with the proapoptotic and cell-cycle checkpoint protein, Rad9

Shuang Lin Xiang, Tomoyasu Kumano, Shu ichi Iwasaki, Xiangao Sun, Kastuji Yoshioka, Ken chi Yamamoto

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Human Rad9 is a key cell-cycle checkpoint protein that is postulated to function in the early phase of cell-cycle checkpoint control through complex formation with Rad1 and Hus1. Rad9 is also thought to be involved in controlling apoptosis through its interaction with Bcl-2. To explore the biochemical functions of Rad9 in these cellular control mechanisms, we performed two-hybrid screening and identified Tetratricopeptide repeat protein 2 (Tpr2) as a novel Rad9-binding protein. We found that Tpr2 binds not only to Rad9, but also to Radl and Hus1, through its N-terminal tetratricopeptide repeat region, as assessed by in vivo and in vitro binding assays. However, the in vivo and in vitro interactions of Tpr2 with Rad9 were greatly enhanced by the deletion of its C-terminal J domain or by a point mutation in the conserved HPD motif in the J domain, though the binding of Tpr2 to Rad1 and Hus1 was not influenced by these J-domain mutations. We further found: (1) Rad9 transiently dissociates from Tpr2 following heat-shock or UV treatments, but the mutation of the J domain abrogates this transient dissociation of the Tpr2/Rad9 complex; and (2) the J domain of Tpr2 modulates the cellular localization of both Tpr2 itself and Rad9. These results indicate that the J domain of Tpr2 plays a criticai role in the regulation of both physical and functional interactions between Tpr2 and Rad9.

Original languageEnglish
Pages (from-to)932-940
Number of pages9
JournalBiochemical and Biophysical Research Communications
Issue number4
Publication statusPublished - Oct 5 2001
Externally publishedYes


  • Apoptosis
  • Cell cycle checkpoint
  • Chaperone
  • Hus1
  • J domain
  • Rad1
  • Rad9
  • Tetratricopeptide repeat

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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