Analysis of genes involved in proliferation and differentiation of megakaryopoiesis using a human megakaryoblastic leukemia cell line

用12-O-十四烷酰-佛波醇-13-乙酸酯（TPA）诱导人急性巨核细胞白血病细胞系（MEG-01）成熟，观察c-abl、c-fos、c-sis和myc基因家族（c-myc、L-myc和N-myc）的表达。在成熟诱导后，c-myc癌基因在细胞系中的组成型表达迅速下降，并在4 h内变得相当不可检测。c-myc的水平在24小时后在MEG-01细胞中完全恢复，而在NOMO-1细胞（一种人急性单核细胞白血病细胞系）中仍然检测不到。TPA处理后15 min内C-fos RNA被诱导，1h达到最高转录水平，此后下降。c-abl、L-myc和N-myc在未诱导和诱导条件下均未检测到表达。放线菌素D处理TPA诱导的细胞对MEG-01细胞中c-myc表达的诱导减少没有影响，而放线菌素D的存在降低了NOMO-1细胞中c-myc转录本的稳定性。DNA酶I处理未诱导和诱导的细胞系的核酸DNA表明，在NOMO-1细胞中，c-myc基因5'的单个DNA酶I超敏感位点的丢失伴随着c-myc表达的降低。

Expression of c-abl, c-fos, c-sis and myc gene family (c-myc, L-myc and N-myc) was examined during 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced maturation in a newly established human acute megakaryoblastic leukemia cell line (MEG-01), which shows dominant morphological changes and/or productions of cell lineage specific functional proteins after TPA treatment. Upon maturation induction, constitutive expression of c-myc oncogene in the cell line was rapidly decreased and become fairly undetectable within 4 h. The level of c-myc was fully recovered after 24 h in MEG-01 cells, whereas it remained undetectable in NOMO-1 cells, a human acute monoblastic leukemia cell line. C-fos RNA was induced within 15 min after TPA treatment, reached to the maximum transcriptional level in 1 h and thereafter decreased. Expression of c-abl, L-myc and N-myc was detected in neither uninduced nor induced condition. Actinomycin D treatment on TPA-induced cells made no effect on the induced reduction of c-myc expression in MEG-01 cells, whereas the stability of c-myc transcripts in NOMO-1 cells was decreased by the presence of actinomycin D. DNAse I treatment of nucleic DNA of both uninduced and induced cell lines showed that the loss of a single DNAse I hypersensitive site 5' of the c-myc gene was accompanied with reduced c-myc expression in NOMO-1 cells.