Question: What histone variants play a role in the DNA damage reponse?

Context:
H2A.Z is an evolutionarily ancient and highly conserved H2A variant that regulates processes ranging from gene expression to the DNA damage response
activation of DNA damage checkpoints (ataxia telangiectasia mutated (ATM) and H2A histone family, member X (H2AFX (H2AFX)))
the specialization imparted by histone H2A (H2A.X and H2A.Z) variants to the nucleosome core particle constitutes the earliest response to DNA damage in the cell
histone variants (H2AX and H2A.Z), histone post-translational modifications (acetylation, phosphorylation, methylation and ubiquitination) and chromatin-remodeling complexes (INO80, SWR1, SWI/SNF, RSC and NuRD) are important and direct players in the DNA double-strand break (DSB)
H2A.Z incorporation in the coding regions of genes encoding proteins involved in the regulation of meiosis and genotoxic stress responses
 phosphorylation of H2AX, a DNA damage signal
DSB) are generally considered the most critical lesion induced by ionizing radiation (IR
phosphorylated forms of histone H2AX 
H2AX has a complete SQ(E/D)varphi (where varphi denotes a hydrophobic residue) known to be phosphorylated in response to DNA damage
H2A.X, plays a very important role in the cellular response to DNA damage
H2A.X is an H2A variant present in multicellular organisms that is specifically phosphorylated on the serine in the C-terminal consensus sequence, canonically "SQEY," in response to DNA damage.
H2AFX) is important in maintaining chromatin structure and genetic stability
Saccharomyces cerevisiae, the linker histone HHO1 is involved in DNA repair
H1 variant, H1R is involved in DNA damage response
high levels of histone H2AX phosphorylation and an increased incorporation of the Htz1p histone variant into chromatin surrounding the DSB
TRF2 upregulation was more dramatic in drug-resistant cells and occurred before the expression of ATM, gammaH2AX and p53
DNA double-strand breaks induced by anticancer drugs or irradiation increase TRF2 expression
Histone variant H2AX and core histone H2A are phosphorylated in mammals and budding yeast, respectively. We demonstrate the DSB-induced phosphorylation of histone variant H2Av in Drosophila melanogaster
formation of a double-strand break (DSB) in chromosomal DNA is highly conserved
H2A variants, H2AX and H2AZ. H2AX is phosphorylated on a serine four residues from the carboxyl terminus in response to the introduction of DNA double-strand breaks
In response to IR, ZNF668 knockdown reduces Tip60-H2AX interaction and impairs IR-induced histone H2AX hyperacetylation, thus impairing chromatin relaxation.
RPA foci formation were reduced in parallel with increasing levels of H2AX phosphorylation
H2AX phosphorylation on a C-terminal serine residue to form "γ-H2AX" is a critical early event in the chromatin response to chromosomal DNA double strand breaks in eukaryotes
The phosphorylation of the histone variant H2AX (gammaH2AX) is one of the best examples of histone PTMs in response to DNA damage induction
One of the most well-characterized modifications is caused by the formation of DNA double strand breaks (DSBs), resulting in phosphorylation of histone H2AX (the so-called gamma-H2AX) on the chromatin surrounding the DNA lesion
H2AX appears to be mainly associated with maintaining the genome integrity by participating in the repair of the double-stranded DNA breaks exogenously introduced by environmental damage (ionizing radiation, chemicals) or in the process of homologous recombination during meiosis
The sustained localization of BMI1 to damage sites is dependent on intact ATM and ATR and requires H2AX phosphorylatio
unique functional interactions among various chromatin modifiers, suggesting new regulatory pathways, such as a heterochromatin-specific modulation of DNA damage response involving H2A.X and WICH, both enriched in silent domains

Answer: Mostly H2A.X, but H2A.Z and H1R have also been associated to DNA damage
Exact answer: H2A.X, H2A.Z, H1R