A DNA crosslinking drug alters synthesis of several low molecular weight proteins in human lymphoma cells

The cytotoxicity of bifunctional alkylating agents is generally attributed to DNA damage, especially DNA-DNA crosslinking activity. It is unclear how crosslinks or other cellular damage result in cell death. Studies of drug effects at the level of expression of specific gene products may help elucidate the mechanism of cell killing. We examined proteins synthesized in L-phenylalanine mustard treated human lymphoma cells by [³⁵S]methionine labeling and SDS-PAGE. Drug-treated cells showed decreased labeling of proteins in two molecular weight bands of 17 kDa (a doublet) and 12 kDa at 6, 18 and 24 hours after drug removal. One of the components of the 17 kDa doublet has been identified as calmodulin, a calcium binding protein essential to cell cycle progression and survival.