Magnesium is an essential cofactor for the synthesis and salvage of purine and pyrimidine nucleotides. It plays important roles in the structure of nucleic acids and affects their interaction with proteins and other ligands. Magnesium is required for DNA replication, transcription into RNA and translation into protein. In spite of the diverse roles of magnesium in these fundamental processes, metabolic regulation by magnesium has not been observed. Its role in the regulation of cell growth, division and differentiation remains uncertain.