Effects of 3‐Deazaadenosine on Apoptosis‐Related Gene Transcripts in HL‐60 Cells

Abstract: The effect of the transmethylation inhibitor 3‐deazaadenosine on transcription levels of genes associated with apoptosis was investigated in HL‐60 cells. After incubation of HL‐60 cells with 100 μM 3‐deazaadenosine for 45 min., a schedule known to perturb transmethylation metabolites and initiate apoptosis in these cells, a 50% decrease in c‐myc and a 50% increase in bcl‐2 RNA steady‐state levels compared to control cells were observed. Transcription levels of c‐myc continued to decrease after extended exposure to 3‐deazaadenosine, while bcl‐2 mRNA levels dropped to 25% and 30% below those in control cells after 1.5 hr and 3 hr, respectively. The expression levels of the bcl‐2 related bax gene, showed a similar pattern as bcl‐2; a 60% increase was initially measured, but after 1.5 and 3 hr, bax transcripts were 80% and 70% respectively, of those found in untreated cells. Another bcl‐2 related gene, bcl‐x , was previously reported to generate two transcripts in human cells. The long variant bcl‐x 1 acts as bcl‐2 , while the short form bcl‐x s induces apoptosis. We were unable to detect bcl‐x s transcripts in untreated and 3‐deazaadenosine treated cells by the highly sensitive reverse transcriptase polymerase chain reaction method. This suggests that this gene product may not be involved in 3‐deazaadenosine induced apoptosis in HL‐60 cells. Bcl‐x 1 mRNA levels, however, slowly decreased with about 50% after 1.5 or 3 hr 3‐deazaadenosine treatment. It is concluded that 3‐deazaadenosine initiated apoptosis affects c‐myc, bcl‐2, bax and bcl‐x 1 mRNA levels.