Endogenous prNL levels and regulation 6, miR 92-1. (A) CLL B cells express a low level of pVHL. CLL B-cell lysates (n = 6) were analyzed for endogenous expression of VHL by Western blot using an antibody to pVHL. Purified CD19+ B cells were used as control for comparison. Similarly, HIF-1α expression in these CLL B-cell lysates was also examined using a specific antibody to HIF-1α. Actin was used as a loading control. (B) CLL B cells overexpress miR-92-1. Expression levels of mature miR-92-1 in CLL B cells were measured by real-time RT-PCR using specific primers. Total RNA was extracted from the same primary CLL B cells (n = 6) used for the Western blot analysis of pVHL as indicated, and purified CD19+ (> 98%) normal B lymphocytes. The single-tube TaqMan microRNA assays were performed to quantify mature miR-92-1 and normalization was performed with RNU6B in triplicate. Relative expression (fold) was calculated using the comparative Ct method, where the expression of miR-92-1 in normal B cells was arbitrarily chosen as one. For comparison of the microRNA fold levels with the VHL protein expression in these samples, densitometric values of VHL from the CLL B-cell Western blot (panel A) were calculated based on the values from normal B cells (arbitrarily chosen as 100%) and are presented below the miR92-1 fold levels. (C) VHL is a target of miR-92-1. The 3′UTR of VHL enables miR-92-1 regulation. (i) The complementarity between VHL cDNA and miR-92-1 is conserved in human and mouse. (ii) Relative repression of firefly luciferase expression standardized to a transfection control, renilla luciferase. As expected, the mutant completely abolished the detected interaction between miR-92-1 and the 3′UTR of VHL as shown in the last column. Experiments were performed twice in triplicate (N = 6). Data are presented as mean ± 1 SE. (D) Introduction of miR-92-1 reduces pVHL level. 293T cells transfected with increasing amounts of miR-92-1 were analyzed for the expression of VHL by Western blot. Actin was used as the loading control. (E) Inhibitor of miR-92-1 up-regulates pVHL. Primary CLL B cells (n = 3) transfected with the antisense inhibitor of miR-92-1 were analyzed for pVHL by Western blot. Actin was used as the loading control. PBMCs from different patients with CLL are marked by numbers.