Changes in Gene Expression and DNA Methylation of Evolutionarily Young AluY Repeats during Apoptosis of Human K562 Erythro-Myeloblastic Leukemia Cells

Abstract

Using a human K562 erythromyeloblastoid cell culture, we demonstrated changes in gene expression of Alu repeats, members of evolutionarily young AluY subfamilies (human mobile SINE elements), and in the DNA methylation level of AluYb8 during camptothecin (CAM)-induced apoptosis. The AluY-RNA level increased about 10 times 24 h and 20 times 48 h after exposure to CAM vs. proliferating cells. Using methylation-specific (MSP) PCR and high-resolution melting (HRM), we showed that the overall AluYb8-DNA methylation level remained intact throughout the apoptotic stages. Using DNA sequencing after bisulfite conversion, we established that at the CpG site, located in the A'-box of the AluYb8 gene promoter, the methylation level decreased significantly during different apoptotic stages. Apparently, it is reduced CpG methylation at the A'-box of the AluYb8 gene promoter, discovered in this work, that is one of the possible factors which account for increased expression of AluY repeats during K562 cell apoptosis. We assume that increased gene expression of evolutionarily young AluY repeats plays an important role in the implementation of the cellular apoptotic pathway.