A mumber of arsenic-binding proteins identified using the affinity chromatography tandem mass spectrometry approach were of particular interest because of their important biological functions .For example ,DNA-dependent protein kinase, ATP-dependent helicase II (Ku 70),and topoismerase 2 alpha , are involved in DNA repair and maintaining genome stability .several other proteins modulate the redox status of cells , e.g . peroxiredoxin-1 and thioredoxin ,and apoptosis ,e.g.,lamin A and heat shock cognate protein .this work shows that arsenic can bind to these proteins in cells extracts。How arsenic affects the function of these proteins in biological systems will have to be confirmed by studying arsenic interaction with proteins in living cells.