Fig. 1. hTERT is downregulated during NB4-LR1 differentiation. Differentiation (+) of NB4-LR1 cells was obtained by a 72-hour treatment with the combination of ATRA (1 µM) and 8-CPT-cAMP (200 µM). RNA and protein extracts were prepared as described in the Materials and Methods. hTERT mRNA expression was quantified by fluorescence real-time RT-PCR using the LightCycler^® technology and the LightCycler TeloTAGGG hTERT Kit from Roche Diagnostics (Meylan, France). The hTERT level was normalized to the expression of the housekeeping gene porphobilinogen deaminase (PBGD) and expressed as a percentage of that detected in the untreated cells. Western blot analyses were performed using RCK-hTERT and NCL-hTERT antibodies. Positions of the molecular weight markers are indicated on the left. Note that the low molecular weight band on NCL-hTERT blot was not reproducibly detected.