No abstract

ATRX is a tumor suppressor that has been associated with protection from DNA replication stress, purportedly through resolution of difficult-to-replicate G-quadruplex (G4) DNA structures. While several studies demonstrate that loss of ATRX sensitizes cells to chemical stabilizers of G4 structures, the molecular function of ATRX at G4 regions during replication remains unknown. Here, we demonstrate that ATRX associates with a number of the MCM replication complex subunits and that loss of ATRX leads to G4 structure accumulation at newly synthesized DNA. We show that both the helicase domain of ATRX and its H3.3 chaperone function are required to protect cells from G4-induced replicative stress. Furthermore, these activities are upstream of heterochromatin formation mediated by the histone methyltransferase, ESET, which is the critical molecular event that protects cells from G4-mediated stress. In support, tumors carrying mutations in either ATRX or ESET show increased mutation burden at G4-enriched DNA sequences. Overall, our study provides new insights into mechanisms by which ATRX promotes genome stability with important implications for understanding impacts of its loss on human disease.

To detect the expression of miRNA-214 in human gastric cancer cell lines of BGC823, MKN45 and SGC7901, and to identify the effect of miRNA-214 on cell cycle and apoptosis of these cells. Expression of miRNA-214 in human normal gastric mucosal cell line GES-1 and human gastric cancer cell lines was detected by real-time reverse-transcription polymerase chain reaction. Antisense-miRNA-214 oligonucleotides were transfected transiently into gastric cancer cell lines to down-regulate the expression of miRNA-214. The cell cycle and apoptosis were studied by flow cytometry assay. PTEN, one of the target genes of miRNA-214 was detected by using of immunocytochemistry and Western blotting. MiRNA-214 was overexpressed in gastric cancer cell lines of BGC823, MKN45 and SGC7901 compared with normal gastric mucosal cell line GES-1. Antisense-miRNA-214 oligonucleotides significantly down-regulated the expression of miRNA-214, and increased the portion of G1-phase and decreased the portion of S-phase in BGC823 and MKN45 cells. The immunocytochemistry test and Western blotting analysis showed that the down-regulation of miRNA-214 could significantly up-regulate the expression of PTEN in BGC823 and MKN45 cells. MiRNA-214 is overexpressed in human gastric cancer cell lines of BGC823, MKN45 and SGC7901. The down-regulation of miRNA-214 could induce a G1 cell cycle arrest in them, the up-regulation of PTEN maybe one of the mechanism.