Table 1.

Histone variants with known or suspected roles in the DNA damage response or in specific DNA repair pathways. Percent homology indicates the percent similarity in the amino acid sequence of the variants compared to the primary amino acid sequence of canonical histones H2A type 1 for the H2A variants and H3.1 for the H3 variants.

Variant Name	Histone Family	Percent Homology to canonical histone	Endogenous Localization	Involvement in DDR or DNA Repair Pathways	References
H1.2	H1	N/A	Enriched at silenced genes	HR, c-NHEJ, alt-NHEJ, apoptosis	[39,41,48–51]
H1.4	H1	N/A	Enriched at silenced genes	HR, c-NHEJ, alt-NHEJ	[52]
H1.0	H1	N/A	Repetitive DNA elements within the nucleoli; accumulates on silenced genes in non-dividing cells	N/A	[35–37]
H1.10	H1	N/A	Hypomethylated CpG islands and active genes	c-NHEJ	[35,39,51]
H2A.X	H2A	90%	Ubiquitously throughout the genome	HR, c-NHEJ	[59,61,62,65,84–89].
H2A.Z	H2A	60%	Actively transcribing genes and centromeres	BER, HR, c-NHEJ	[90,93,96,98,99]
mH2A	H2A	60%	Barr-body heterochromatin	BER, NER, HR	[110,122,123,125,126]
H2A.B	H2A	50%	Ubiquitously (except in the Barr-body)	N/A	[131,132]
H2A.J	H2A	94%	Enriched in senescent cells with DNA damage	N/A	[140,142]
cenH3	H3	45%	Centromeres	BER, HR	[154,157,159,163,164,167,168]
H3.3	H3	96%	Promoters of transcribing genes, telomeres, pericentromeric, rDNA heterochromatin	NER, HR, c-NHEJ	[169,182–186]
H3.4	H3	97%	N/A	N/A	[190]
H3.5	H3	93%	Euchromatic regions (seminiferous tubules)	N/A	[194,195]
H3.Y.1	H3	72%	Transcription start sites	N/A	[195,196]

N/A = Not applicable.