Abstract
The COP9 signalosome (CSN) is a nuclear protein complex essential for plant and animal development. It has been shown that the N terminus of CSN1 (CSN1N) represses transcription of JNK1 in the JNK1/SAPK signaling pathway. Inhibitory studies suggested that this repression was different from the known proteasome-mediated proteolysis. To further understand this mechanism, interacting proteins (NBPs) directly binding to CSN1N were purified from mammalian cells. SAP130, one of NBPs, is known to be involved in mRNA splicing. SAP130 is a subunit of the SF3b complex that associates with the U2 snRNP complex and the STAGA complex, suggesting that CSN is involved in post-transcriptional regulation.
To characterize this novel function of CSN in the plant kingdom, we have identified the homolog of SAP130 in Arabidopsis (AtSAP130). AtSAP130 was encoded by two genes mapping to chromosome 3 producing identical protein. Here, we will discuss the interaction of CSN1N and AtSAP130.
