RB, epigenetic changes and chromosomal alterations in human primary fibroblasts in culture

The regulation of chromatin structure is a dynamic and complex process modulated by epigenetic mechanisms. Epigenetic changes as malfunctioning of histone modifications and DNA methylation could affect several different cellular processes like regulation of gene transcription and could compromise the correct chromosome condensation and segregation. Is important to note that these alterations have been correlated with cancer initiation/progression. In particular hypomethylation of pericentromeric regions, usually methylated, has been associated to chromosomal instability, as well as hypermethylation of promoter CpG islands of tumor suppressor genes (p16, CHFR, BRCA1) is considered a cause of transcriptional gene silencing observed in many tumors. Dysfunction of the Retinoblastoma gene is associated with altered expression of genes involved in epigenetic processes (i.e. DNMT1, EZH2, BMI1) in tumor cells. To get additional clues on this topic we are investigating the effects of RB stable depletion and DNMT1 transcriptional silencing in primary human fibroblasts (IMR90) in culture Our results show that RB stable depletion leads to up-regulation of DNMT1, DNMT3b, EZH2, and BMI1 genes involved in epigenetic events and it seems to affect global genomic methylation. Moreover we have observed that transient silencing of DNMT1 influences genome stability by modifying centromeric region structure and cell-cycle progression