Effects of SWI/SNF complex on DNA damage repair in heterochromatin of embryonic fibroblast cells

Abstract

Objective

To investigate the impact of SWI/SNF complex on heterochromatin DNA damage repair after exposure to X-ray irradiation, in order to explore the underlying mechanism.

Methods

NIH3T3 and MRC5 cells were treated with 50 ​nmol/L siRNA targeting SWI/SNF complex subunits (BRM, ARID1A, BRG1 and SNF5), and YAP/TAZ. At 24 ​h after transfection, the cells were irradiated with 0.5 and 1 ​Gy of X-rays. At 20, 60 and 240 ​min post-irradiation, γH2AX assay was performed to evaluate the radiation response in total or heterochromatin. Comet assay was used to determine the role of YAP/TAZ in DNA damage when the cells were irradiated with 4 ​Gy of X-rays. NIH3T3 were treated with 50 ​nmol/L siRNA targeting BRM/BRG1 and YAP/TAZ to determine their relationship on heterochromatin DNA damage repair.

Results

In NIH3T3, SWI/SNF complex subunits (BRM, ARID1A and BRG1) knock-down increased γH2AX in total and heterochromatin at 1 ​Gy 60 ​min post-irradiation (P ​< ​0.05), while SNF5 knock-down decreased heterochromatin γH2AX at 1 ​Gy 20 ​min post-irradiation (P ​< ​0.05). In MRC5, BRM and BRG1 knock-down increased γH2AX in total and heterochromatin at 1 ​Gy 60 ​min post-irradiation (P ​< ​0.05). Inconsistently, ARID1A knock-down did not affect it, and SNF5 knock-down increased heterochromatin γH2AX at 1 ​Gy 60 ​min post-irradiation (P ​< ​0.05). Moreover, YAP/TAZ knock-down decreased heterochromatin γH2AX in NIH3T3 and MRC5 (P ​< ​0.05). Meanwhile, YAP/TAZ knock-down decreased Tail Moment in comet assay at 4 ​Gy 60 ​min post-irradiation (P ​< ​0.05). BRM/BRG1 combining with YAP/TAZ knock-down significantly decreased heterochromatin γH2AX compared with single BRM/BRG1 knock-down at 0.5 ​Gy 60 ​min post-irradiation (P ​< ​0.05).

Conclusions

The SWI/SNF complex subunits exhibited varying effects on DNA damage repair. BRM/BRG1 knock-down promoted γH2AX accumulation in heterochromatin through YAP/TAZ. This study provides a novel direction for DNA damage repair and sheds light on the role of SWI/SNF complex in response to DNA damage repair in heterochromatin.