Figure 2. Alba proteins are components of complexes S2 and S3.

(A) A panel of RNAi cell lines was constructed to knock down single Alba proteins or combinations of Alba proteins. A derivative of AnTat 90-13 [36], in which one copy of the GPEET coding region was replaced by enhanced GFP, was used as the parental line for Alba 1, Alba2, Alba1&2 and Alba3&4 RNAi cells. Unmodified AnTat 90-13 was used as the parental line for Alba 3 and Alba4 RNAi cells. RNAi was induced by addition of tetracycline to the cultures 3 days prior to the preparation of protein extracts. Band shift assays with ³²P-labeled GPEET were performed as described in the legend to Figure 1. - Tet: uninduced; + Tet: induced; RNA only: incubation of GPEETLII without protein extract. (B) and (C): Alba1 and Alba2 proteins are dependent on Alba3. Western blot analysis of Alba proteins after knockdown of Alba3 (B) or Alba4 (C) by RNAi. Protein extracts of uninduced (- Tet) and induced (+Tet) cells were prepared every second or third day for 12 days and Alba proteins were detected with specific antibodies. HSP60 served as a loading control.