DNA Methylation and Chromatin Remodeling

Three highly significant studies over the last few years have revealed additional links between DNA methylation and chromatin structure other than the previously described interactions between DNMTs and HDACs and histone tail modifications. While covalent modification of the core histone tails by acetylation, methylation, and phosphorylation is a major method of regulating chromatin structure, another mechanism involves ATP-dependent chromatin remodeling machines. These remodeling enzymes, or...

Causes of Altered DNA Methylation in Urological Cancers

The causes of altered methylation may be distinct in different cancers (Fig. 2). In some cancers, apparently aberrant methylation may in fact largely reflect the methylation pattern of the affected stem cell. Thus, different germ cell tumors display methylation patterns at imprinted genes corresponding to distinct stages of germ cell development.8,10,14 Conversely, failure to set up proper methylation patterns of mature cells may underlie blocked differentiation. Clear-cell renal carcinomas may...

Are There Tumor Specific DNA Hypomethylation Profiles Like the Tumor Specific DNA Hypermethylation Profiles

Hypermethylation in cancer has most often been described for the CpG-rich regions (CpG islands) that overlap many promoters.17,35,36 While disparate types of cancer may display hypermethylation of the same promoters, nonetheless there are highly significant differences in the methylation frequencies for CpG islands between tumor types.17 As for DNA hypomethylation associated with cancer, cancer-linked hypermethylation probably involves much overshooting in terms of targets that function in...

Is DNA Hypomethylation Like DNA Hypermethylation Sometimes Associated with Tumor Progression

Hypermethylation of a subset of CpG islands is progressive in some types of cancer although sometimes this regional hypermethylation occurs very early in tumorigenesis, and other times it can serve as a significant indicator of survival.16,82, 3 Also, DNA hypomethylation is sometimes associated with tumor progression as seen in studies of repeated DNA sequences. In a study of 31 hepatocellular carcinomas by Itano and coworkers,84 the degree ofhypomethylation of either of two repetitive...

DNA Methylation and Disease

The progress made in our understanding of the methylation machinery, its role in important developmental processes such as genomic imprinting and X-chromosome inactivation, the involvement of DNA methylation in the control of the cell cycle, in the process of cell differentiation, in host defense and gene silencing can now be used in deciphering the molecular events that lead to disease. Since DNA methylation in cancer is the theme of this book, I will not dwell on this important involvement of...