Molecular mechanisms of gene silencing mediated by DNA methylation

Michela Curradi, Annalisa Izzo, Gianfranco Badaracco, Nicoletta Landsberger

Research output: Contribution to journalArticlepeer-review

Abstract

DNA methylation and chromatin modification operate along a common pathway to repress transcription; accordingly, several experiments demonstrate that the effects of DNA methylation can spread in cis and do not require promoter modification. In order to investigate the molecular details of the inhibitory effect of methylation, we microinjected into Xenopus oocytes a series of constructs containing a human CpG-rich sequence which has been differentially methylated and cloned at different positions relative to a specific promoter. The parameters influencing the diffusion of gene silencing and the importance of histone deacetylation in the spreading effect were analyzed. We demonstrate that a few methylated cytosines can inhibit a flanking promoter but a threshold of modified sites is required to organize a stable, diffusible chromatin structure. Histone deacetylation is the main cause of gene repression only when methylation does not reach levels sufficient to establish this particular structure. Moreover, contrary to the common thought, promoter modification does not lead to the greater repressive effect; the existence of a competition between transactivators and methyl-binding proteins for the establishment of an open conformation justifies the results obtained.

Original languageEnglish
Pages (from-to)3157-3173
Number of pages17
JournalMolecular and Cellular Biology
Volume22
Issue number9
DOIs
Publication statusPublished - 2002

ASJC Scopus subject areas

  • Cell Biology
  • Genetics
  • Molecular Biology

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