The cellular response to DNA damage involves extensive interaction with and manipulation of chromatin. This includes the detection and repair of the DNA lesion, but there are also transcriptional responses to DNA damage, involving the up- or down-regulation of numerous genes. Therefore changes to chromatin structure, including covalent modification of histone proteins, are known to occur during DNA-damage responses. One of the most well characterized DNA-damage-responsive chromatin modification events is the phosphorylation of the SQ motif found in the C-terminal tail of histone H2A or the H2AX variant in higher eukaryotes. In the budding yeast, a number of additional residues in this region of histone H2A that contribute to the cellular response to DNA damage have been identified, providing an insight into the nature and complexity of the DNA-damage histone code.