Abstract
COP9 signalosome (CSN) is a conserved nuclear complex essential for survival. CSN regulates proteolysis of nuclear proteins by deconjugating RUB1 from the cullin subunit of CRL-type E3 ligases.
Since the N-terminal of CSN1 subunit harbored transcriptional repression activity, we isolated proteins interacting with this region, and identified SAP130, DdxX15, and CF Im68, which are all involved in mRNA processing.
Although, detailed function of SAP130 is unknown, SAP130 has been identified in the SF3b splicing complex and STAGA/TFTC transcription complexes. Based on our hypothesis that CSN-SAP130 interaction is the key to bridge proteolysis and mRNA processing, we first revealed that SAP130 binds CSN in human and plants. We further showed SAP130 also binds CRL-type E3 ligases, implying novel regulation of CSN.
Currently genetic/reverse-genetic approaches are applied in plants to reveal the CSN-SAP130 function in vivo. Here we will discuss the conservation and specificity of CSN regulation among kingdoms.
