科研之友
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摘要
Despite considerable work on the epigenetic control of tumor suppressor genes, little is known about the potential role of promoter CpG demethylation in the activation of oncogenes in lymphoid tumors. The HOXII proto-oncogene is frequently activated in T-cell acute lymphoblastic leukemia (T-ALL). HOXII activation can occur in the absence of translocation of the gene to the T-cell receptor locus (Salvati et al., 1995), implying that activation mechanisms must be involved other than the juxtaposition of the gene to adjacent enhancing sequences. We tested whether the methylation status of the proximal promoter was correlated with expression status in T-ALL and found that, in all cases, expression of HOXII in T-ALL was associated with extensive demethylation of the proximal HOXII promoter, regardless of whether or not translocation was involved. In contrast, cells that did not express HOXII showed a more methylated pattern of CpG residues in the proximal promoter. Methylation of this sequence in vitro was sufficient to silence the proximal promoter. We propose a model in which the selection of leukemia clones via a pathway involving HOXII expression requires the demethylation of its promoter as a prerequisite for additional gene activation mechanisms.
- 出版日期2000-12
