[Epigenetic activation of IGF2 during cellular senescence]

Epigenetic regulations of insulin-like growth factor 2 (IGF2) were observed during cellular replicative senescence and premature senescence induced by hydrogen peroxide of human embryonic lung fibroblasts (HEFs).

The mRNA level of IGF2 was detected by Q-PCR. The methylation status in the promoter region was observed by methylation-specific PCR. The histone modifications was detected by chromatin immunoprecipitation-Q-PCR assay, including acetylation for H3, H4 and methylation for H3 ( Lys4) and H4 (Lys20).

In the process of cellular senescence, the mRNA level of IGF2 increased in both mid-aged and replicative senescent cells, but increased obviously in premature senescent cells compared with that of young cells. In the promotor region from -658 bp to -456 bp, the methylation level for IGF2 was detected only in replicative senescent cells. About the main histone modifications, IGF2 in the region (-856 bp - -634 bp) was H4 acetylation and H3K4 methylation in replicative senescence, while in the region (+9 bp - +145 bp) was H3K4 and H4K20 methylation in replicative senescence and H3K4 methylation in premature senescence.

The histone modifications take part in regulating the mRNA expression for IGF2 during cellular senescence and different mechanisms exist between two types of senescence.