Table 1.

Deposition, localization, and functional properties of histone variants implicated in human cancer

Variant	Function	Chaperones and regulatory factors	Distribution patterns	Deposition	Mutant phenotype
H2A variant
H2A.Z (H2A.Z.1, H2A.Z.2 and H2A.Z.2.2)	Transcriptional regulation (mostly activation) Genome stability and chromosome segregation Telomere stability (S. cerevisiae) Others	SRCAP complex p400 complex (including Tip60) INO80 (negative regulator, S. cerevisiae)	TSSs, enhancers, insulators Pericentric chromatin Subtelomeric regions (S. cerevisiae)	Replication-independent	T.thermophila, D. melanogaster, X. Laevis, M. musculus: lethal (H2A.Z.1) S. cerevisiae, S. pombe: transcriptional defects, chromosmome loss (H2A.Z.1)
H2A.X	DSB repair factor recruitmenta Meiotic gene silencinga (M. musculus)	Tip60 (D.melanogaster) FACT Nucleolin	Genome-wide DSB sitesa	Replication-independent DSB-induced (IRIF)a	M. musculus: chromosomal aberrations
mH2A (mH2A.1 and mH2A.2)	Transcriptional regulation (mostly repression)	ATRX (negative regulator)	Upstream and downstream of TSS Telomeres SAHFs Xi	Replication-independent	D. rerio: brain developmental defects (mH2A.2) M. musculus: female liver steatosis (mH2A.1)
H3 variant
CENP-A	Centromere structure and function Kinetochore assembly (chromosome segregation)	HJURP Mis18 complex	Centromeres	Replication-independent (M/G1)	M. musculus: lethal
H3.3	Gene activation Telomere homeostasis Epigenetic memory (X. laevis) Spermatogenesis (D. melanogaster)	ATRX-Daxx HIRA DEK	Euchromatin (active genes) Promoters and regulatory sequences Telomeric repeats Pericentric heterochromatin	Replication-independent	D. melanogaster, T. thermophila: sterility M. musculus (hypomorphic allele): lethality or fertility defects

All data refer to mammalian histone variants, unless otherwise specified

^aγ-H2A.X