Fig. 8. SIAH1 is regulated at the transcriptional level. (A) BOB.1/OBF.1 protein levels from BCR cross-linked Ramos B cells were analyzed by western blotting. RelA was used as a loading control. (B) RNA from the same cells used in (A) was transcribed into cDNA and SIAH1 expression was analyzed by LightCycler PCR. (C) The cDNAs from CD38^– and CD38⁺ tonsillar B cells, already used in Figure 1A, were analyzed for SIAH1 expression by LightCycler PCR. (D) Potential altered interaction of BOB.1/OBF.1 and SIAH1 in CD38^– and CD38⁺ tonsillar B cells was analyzed by pull-down assays. Therefore, the GST–SIAH1 C-terminal and the GST–SIAH1 N-terminal part were mixed with lysates from CD38^– and CD38⁺ tonsillar B cells.