DNMT1 depletion activates a pathway p14ARF/TP53 controlled that induces G1 arrest preventing DNA demethylation and aneuploidy

Background: Aneuploidy is considered the result of chromosome segregation errors caused by defects in the mitotic spindle assembly, centrosome duplication, cell-cycle checkpoints and epigenetic changes. Usually, aneuploidy affects negatively proliferation of normal cells. However, it is frequently associated with cancer that is characterized by a uncontrolled proliferation. Thus, understanding the pathway(s) that block proliferation of aneuploid cells might open new avenue to exploit new cancer therapies. O bservations: We found that in primary human fi broblasts (IMR90) knocking down of DNMT1, a member of epigenetic machinery is perceived by the cell as a stress signal that induces p14ARF activation followed by TP53 stabilization that in turn transactivates p21waf1 triggering the G1 arrest. DNMT1 depleted cells bypassed the arrest and became aneuploid when TP53 or p14ARF were simultaneously silenced by RNAi. In addition by using stable near-diploid human tumor cells (HCT116), which are p14ARF-null and TP53-wt, we found that DNMT1 depleted HCT116 cells did not arrest in G1, underwent overall DNA demethylation and become aneuploid. C onclusions: Our results suggest that Dnmt1 depletion triggered G1 arrest in human fi broblasts by activating a pathway p14ARF/ TP53 dependent thus avoiding aneuploidy caused by DNA demethylation coupled with incorrect cycle progression.