Extranodal NK/T-Cell Lymphoma, Nasal Type, Presenting as Facial Cellulitis

Background: Checkpoint kinase 1 (CHK1) is a serine/threonine-protein kinase which plays a major role during checkpoint-mediated cell cycle arrest and activation of DNA repair in response to DNA damage. Ultraviolet (UV) irradiation induces DNA damage triggering the cell cycle arrest and the cell may be forced into apoptosis if damage is not repaired. Through phosphorylation mediated activation CHK1, as an effector kinase, responds to this damage by targeting downstream effector proteins. Objective: The objective of the present study was to demonstrate CHK1 methylation in response to UV induced DNA damage. Methods: Expression of CHK1 was detected in a cancer cell line Hct-116. Hct-116 cells, cultured in RPMI-1640 medium supplemented with serum and antibiotics, were transfected with HA-Chk1 plasmid, exposed to UV radiation and incubated for different time intervals. Cell lysis followed by immunoblotting was performed to visualize the signals of methylated CHK1. Result: Methylated CHK1 signals were observed in response to UV induced DNA damage in a cancer cell line Hct-116. Expectedly, it was found that with the increased duration of post UV exposure, methylation level of CHK1 was also amplified. Discussion and Conclusion: Here, for the first time, it is reported that DNA damage induced by UV radiation was associated with elevated methylation of CHK1. This new finding might indicate that cells may have evolved mechanisms to promote CHK1 methylation for reasons not yet known. This study reveals novel modification of CHK1 as a component of the cellular response to DNA damage which may help us understand the importance of such modifications.