|P.1477 left column 2nd paragraph: "The enormous investment that cells are prepared to make in genome maintenance is illustrated by the class of repair proteins that can be used only once. For instance, O-6-methylguanine-DNA methyltransferase repairs a single O-6-methylguanine lesion by transferring the methyl from a guanine in DNA to a cysteine in the enzyme, thereby inactivating itself [ref 21]. Similarly, recognition of a UV-induced dimer in DNA by nucleotide-excision repair may require the sacrifice of a UV DNA damage binding protein 2 (xeroderma pigmentosum group E) [refs 22, 23]. Moreover, DNA damage induces well over 900 distinct phosphorylation events involving more than 700 proteins [ref 24] repair of a single double-strand break may require more than 10^4 ATP molecules, which are used in signaling, the generation of repair foci, and the formation of the RAD51 nucleofilament, an intermediate in recombination repair. The complexity of genome maintenance underscores the importance of preserving genome integrity."