Pan Q, Simpson R U
Department of Pharmacology, University of Michigan, School of Medicine, 1301 MSRB III, 1150 West Medical Center Drive, Ann Arbor, Michigan 48109-0632, USA.
J Endocrinol. 2001 Apr;169(1):153-9. doi: 10.1677/joe.0.1690153.
The expression of c-myc is decreased by 1,25-(OH)2D(3) during HL-60 cell differentiation. Concomitantly, 1,25-(OH)2D(3) increases the expression and DNA binding activity of HOXB4, a homeobox gene. HOXB4 binds to the c-my c gene at sites involved in blocking c-myc transcription elongation. In this study, a phosphorothioate antisense oligonucleotide targeted against HOXB4 was examined for its effect on 1,25-(OH)2D(3) inhibition of c-myc expression. Alone, 1,25-(OH)2D(3) (20 nM) increased HOXB4 levels by 103+/-7% (mean+/-s.e., n=3) and decreased c-myc levels by 89+/-5% (mean+/-s.e.m., n=3) at 48 h of treatment. HOXB4 antisense treatment completely blocked the induction of HOXB4 by 1,25-(OH)2D(3). In addition, HOXB4 antisense partially blocked 1,25-(OH)2D(3)-mediated decrease in c-myc levels (46+/-6% inhibition) and promotion of HL-60 cell differentiation (20+/-2% and 25+/-3% inhibition as assessed by nitroblue tetrazolium and non-specific esterase assays respectively). The data further establish that HOXB4 levels are regulated by 1,25-(OH)2D(3) and reveal that HOXB4 participates in the down-regulation of c-myc expression.
在HL-60细胞分化过程中，1,25-(OH)₂D₃可降低c-myc的表达。同时，1,25-(OH)₂D₃可增加同源框基因HOXB4的表达及DNA结合活性。HOXB4在参与阻断c-myc转录延伸的位点与c-myc基因结合。在本研究中，检测了针对HOXB4的硫代磷酸酯反义寡核苷酸对1,25-(OH)₂D₃抑制c-myc表达的影响。单独使用时，1,25-(OH)₂D₃（20 nM）在处理48小时后可使HOXB4水平升高103±7%（平均值±标准误，n = 3），并使c-myc水平降低89±5%（平均值±标准误，n = 3）。HOXB4反义处理完全阻断了1,25-(OH)₂D₃对HOXB4的诱导。此外，HOXB4反义处理部分阻断了1,25-(OH)₂D₃介导的c-myc水平降低（46±6%抑制）以及HL-60细胞分化的促进作用（分别通过硝基蓝四唑和非特异性酯酶测定评估，抑制率分别为20±2%和25±3%）。这些数据进一步证实HOXB4水平受1,25-(OH)₂D₃调控，并揭示HOXB4参与了c-myc表达的下调。
