title: The meaning of the methylation of genomic DNA in the regulation of gene expression levels.
abstract: BACKGROUND
  Methylation of genomic DNA is one of the major mechanisms that deactivates genes and regulates their tissue-specific transcription levels. Its patterns are based on clonal inheritance that occurs in the early stages of embryogenesis. All changes in the DNA methylation levels occurring especially in the promoter region of the genes, which involve hypo- as well as hyper-methylation, lead to cell differentiation and growth disorders. Therefore it can become an impulse that initiates different pathological processes including carcinogenesis.
  
  
  METHODS
  The purpose of this review was to present the recent knowledge concerning methylation of genomic DNA based on recent references and authors' experience.
  
  
  CONCLUSIONS
  Genome stability disorders could be caused either by mutations, which damage the structure of the genes and have not been formerly removed, or as the consequence of an epigenetic mechanism. Methylation plays a decisive role in the activity of many genes and could be a natural weapon of an organism against the expression of foreign genetic material that degrades the original genome structure.
authors.affiliation: 2nd Department of Gynaecology and Obstetrics, Wroclaw Medical University, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Popiela
authors.forename: G
authors.initials: G
authors.lastname: Keith
authors.forename: A
authors.initials: A
authors.lastname: Borzecki
authors.forename: G
authors.initials: G
authors.lastname: Popiela
authors.forename: M
authors.initials: M
authors.lastname: Manowiec
authors.forename: M
authors.initials: M
authors.lastname: Gabrys
mesh_terms: D019175:DNA Methylation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009369:Neoplasms / Q000235:genetics*