Fig. 2. Arabidopsis CSN3 is a subunit of the COP9 signalosome. (A) Arabidopsis CSN3 co-fractionates with the COP9 signalosome. CSN3 co-fractionated with other known COP9 signalosome subunits in a peak around 500 kDa in wild type but was absent in the fus11-U203 mutant. Total soluble protein extracts from 6-day-old light-grown wild-type seedlings (WT) and 8-day-old light-grown fus11-U203 seedlings were separated using a Superose 6 HR gel filtration column, followed by SDS-PAGE and protein blot analysis with antibodies against CSN1, CSN3 and CSN5 as indicated on the left. The plant materials used are indicated on the right. (B) Arabidopsis CSN3 co-immunoprecipitates with other known COP9 signalosome subunits. The antibodies used for immunoprecipitation from the total soluble proteins are indicated on the top. The antibodies used in the immunoblots are labeled on the right. ‘PI IP’ is the preimmune serum from the same rabbit before immunization and was used as negative control. The immunoprecipitates were separated using 10% SDS-PAGE and probed with antibodies against CSN1, CSN3 and CSN5.
