IER5 Negatively Regulates Cdc25B Expression in HeLa Cells After Gamma Ray Irradiation

Radiotherapy is commonly used to treat many cancers, and their sensitivity to radiation is crucial for favorable outcomes. This study investigated whether the immediate early response 5 (IER5) protein affects Cdc25B protein expression in HeLa cells after gamma irradiation. IER5 was knocked down using RNA interference (RNAi) in HeLa cells irradiated with 2 or 4 Gy of gamma rays. The mRNA and protein expression levels were subsequently determined via qRT-PCR and western blotting. The distribution of cells during the cell cycle was also determined using flow cytometry. IER5 protein levels were successfully reduced with RNAi. Variations in IER5 levels led to differences in Cdc25B mRNA and protein levels. Moreover, IER5 affected the proportion of cells in the G2 phase, which is regulated mainly by Cdc25B. Pearson correlation analysis was conducted on the expression levels of IER5 and Cdc25B in HeLa cells and the IER5-silenced HeLa (siIER5-HeLa) cell line at various time points after exposure to 4 Gy of gamma rays, and a negative correlation was detected between IER5 and Cdc25B expression levels, with correlation coefficients of -0.686 and -0.663, respectively. Additionally, variations in IER5 levels led to differences in the expression levels of p53, NF-YB, and p300, which may be putative transcriptional regulators of Cdc25B. These results suggest that IER5 plays a negative role in regulating Cdc25B expression, which may involve interactions with the transcriptional regulators p53, NF-YB, and p300.