The COP9 signalosome (CSN) is a multiprotein complex which participates in diverse cellular and developmental processes. CSN1, one of the subunits of CSN, is essential for assembly of the multiprotein complex via PCI (proteasome, COP9 signalosome and initiation factor 3) domain in the C-terminal half of CSN1. However, the role of the N-terminal domain (NTD) of CSN1, which is critical for the function of CSN, is not completely understood. Using a yeast two-hybrid (Y2H) screen, we found that the NTD of CSN1 interacts with TSK-associating protein 1 (TSA1), a reported Ca2+-binding protein. The interaction between CSN1 and TSA1 was confirmed by co-immunoprecipitation in Arabidopsis. tsa1 mutants exhibited a short hypocotyl phenotype in darkness but were similar to wild-type Arabidopsis under white light, which suggested that TSA1 might regulate Arabidopsis hypocotyl development in the dark. Furthermore, the expression of TSA1 was significantly lower in a csn1 null mutant (fus6), while CSN1 expression did not change in a tsa1 mutant with weak TSA1 expression. Together, these findings suggest a functional relationship between TSA1 and CSN1 in seedling development.
[1]Peking Univ, Peking Yale Joint Ctr Plant Mol Genet & Agrobiote, Dept Biochem, Coll Life Sci, Beijing 100871, Peoples R China;
[2]Fudan Univ, State Key Lab Genet Engn, Dept Biochem, Shanghai 200433, Peoples R China;
[3]Beijing Normal Univ, Beijing Key Lab Gene Engn Drug & Biotechnol, Dept Biochem, Coll Life Sci, Beijing 100875, Peoples R China;
[4]Yale Univ, Dept Mol Cellular & Dev Biol, New Haven, CT 06520 USA
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