We have overexpressed Chk1 to rescue the defective Chk1 function which may not be identical to impaired Chk1 phosphorylation. Nonetheless, the ultimate purpose of this experiment was to restore the function of Chk1, which was reflected by the phosphorylation of Chk1 on S345, an indicator of the functional activation of Chk1, in Chk1 overexpressing cells. Chk1 overexpression has been also used previously to restore G2 checkpoint function. Taken together, these results demonstrated the pivotal role of defective Chk1 function in G2 checkpoint deficiency in LMP1- expressing nasopharyngeal epithelial cells in response to DNA damage. Since Chk1 also functions in S phase checkpoint, the possible role of LMP1 in inducing defect in S phase checkpoint is under active investigation in our laboratory. In summary, we have provided the first evidence that LMP1 enhances the formation of c-ray-induced chromatid breaks in metaphases of human nasopharyngeal epithelial cells by impairing G2 checkpoint function. These unrepaired chromatid breaks may be lost from daughter cells. This study suggests that LMP1 expression could induce genomic instability in nasopharyngeal epithelial cells under genotoxic stress, which is continuously faced by human cells. Further studies on the impact of interaction between genotoxic microenvironment and EBV infection on NPC pathogenesis are warranted. Membrane proteins are at the interface between the cell and its external environment making them instrumental in synaptic and neuronal transmission via cell adhesion, cellular trafficking, and ion transport. These processes are known to be disrupted in neuropathological disorders such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Furthermore, membrane proteins constitute one-third of the total proteins encoded by the human genome making them important pharmacological and biomarker targets for drug development. Intriguingly, greater than 60% of the major pharmaceutical drug targets are known membrane proteins, emphasizing their crucial role in cellular dynamics and disease processes. Despite years of extensive research, comprehensive AbMole BioScience Life Science Reagents analysis of membrane proteins is challenging to say the least. Integral membrane proteins are defined as transmembrane proteins, with a hydrophobic domain that interacts directly with the hydrophobic core of the lipid bilayer. Thus making analysis by conventional 2-D gel-based techniques difficult due to their poor solubility, basic pH, low molecular weight, and tendency to aggregate out of solution. As a consequence, membrane protein analysis is often approached by an enrichment process followed by tryptic digestion and analysis at the peptide level by LC-MS/MS. Strategies traditionally used for enriching for membrane proteins, include 1) sub-cellular fractionation with a series of centrifugations, or with a sucrose density gradient centrifugation, 2) delipidation to remove the lipid bilayer surrounding the transmembrane helices, 3) affinity purification, and 4) removal of non-membrane proteins using high salt and high pH.