Reports from University Leipzig advance knowledge in gene therapy
2007 NOV 19 -- Investigators publish new data in the report 'Cell cycle-dependent transcription of cyclin B2 is influenced by DNA methylation but is independent of methylation in the CDE and CHR elements.' "DNA methylation is an important mechanism involved in embryogenesis and tumor development. Changing cytosines to 5-methylcytosines in CpG dinucleotides has been found to be responsible for the inactivation of tumor suppressor genes by repressing transcription," scientists writing in the FEBS Journal report. "A central cell cycle regulator whose synthesis is controlled by transcription is cyclin B. In mammalian cells, cyclin B1 and B2 proteins are well characterized and often found to be overexpressed in cancer patients. Transcription from cyclin B1 and B2 promoters during the cell cycle is dependent upon a combination of two sites named 'cell cycle-dependent element' (CDE) and 'cell cycle genes homology region' (CHR), through repression in G(0) and G(1) followed by release in G(2)/M. Here we show that the cyclin B2 promoter contains a CpG island and that 5-aza-deoxycytidine treatment leads to deregulation of cell cycle-dependent mRNA expression from this gene via a loss of repression in G(0). Furthermore, deletion of the DNA methyltransferase genes DNMT1 and DNMT3b leads to an increase in transcription of cyclin B2. Additionally, DNA methylation in vitro prevents transcriptional activation of the cyclin B2 promoter in G(2)/M. Analysis in vivo of the cyclin B2 core promoter revealed that the CDE/CHR site is partially methylated. However, quantitative in vivo analysis of the CpG-methylation level of the CDE during cell division indicates that CpG methylation is independent of the cell cycle," wrote K. Tschöp and colleagues, University Leipzig. The researchers concluded: "We conclude that DNA methylation affects cell cycle-dependent transcription of cyclin B2 but that regulation through CDE/CHR is independent of cytosine methylation." Tschöp and colleagues published their study in FEBS Journal (Cell cycle-dependent transcription of cyclin B2 is influenced by DNA methylation but is independent of methylation in the CDE and CHR elements. FEBS Journal, 2007;274(20):5235-49). Additional information can be obtained by contacting K. Tschöp, Interdisziplinares Zentrum fur Klinische Forschung, Medizinische Fakultat, Universitat Leipzig, Germany. The publisher of the FEBS Journal can be contacted at: Blackwell Publishing Ltd., 9600 Garsington Rd., Oxford OX4 2DG, Oxon, England. Keywords: Germany, Biotechnology, Cell Biology, DNA, Gene Therapy, Genetics, Genomics, Oncology, Tumor Suppression. This article was prepared by Clinical Oncology Week editors from staff and other reports. Copyright 2007, Clinical Oncology Week via NewsRx.com.
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