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Research Paper
Expression Analysis of the Epigenetic Methyltransferases and Methyl-CpG Binding Protein Families in the Normal B-cell and B-cell Chronic Lymphocytic Leukemia (CLL)
Harikrishnan KN, Sahar Bassal, Chris Tikellis and Assam El-Osta
volume 3 | issue 10
october 2004Pages: 989-994
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The importance of epigenetic modifications in carcinogenesis has been a source of controversy for some time. There is little doubt that changes in genomic hypermethylation contribute to the silencing of tumour suppressor genes. Furthermore, recent studies have also identified the significance of genomic hypomethylation associated with chromosomal instability and tumourigenesis. One of the most perplexing questions regarding epigenetic modifications and leukemogenesis is the relationship with DNA methyltransferases (DNMT’s). The primary function of the DNMT enzymes is to methylate genomic DNA, whereas the methyl-CpG binding domain proteins (MBD) interpret this methylation signal and regulate gene expression and chromatin behaviour. In this study we analyse these gene families by quantitative real-time PCR to investigate whether expression levels and the B-cell chronic lymphocytic leukemia (B-CLL) phenotype are associated. Furthermore, given the epigenetic crosstalk between genome stability and the histone chromatin code we have analysed eukaryotic histone methyltransferase (Eu-HMTaseI). Surprisingly, we did not observe significant changes in DNMT1 expression in B-CLL cases when compared to normal lymphocytes, regardless of whether we normalise against GAPDH or PCNA as reference standards. Indeed, expression of the maintenance and de novo methylases were independently regulated. Of particular note was the significant down regulation of DNMT3b. Furthermore, we observed a positive correlation between HMTaseI expression levels and stage of leukemia suggesting that changes in the methylation patterns in B-CLL may represent deregulation of the epigenetic repertoire that also include the methylation dependent binding proteins, MBD2 and MeCP2. We envisage changes in the epigenetic program are multifactorial in nature and postulate that the prevalent genomic methylases just one component of a larger epigenetic repertoire.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDFIf the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.