Table 2. Effects of Environmental Chemicals on Histones.

Exposure	+/-	Modification	Type	Tissue	Ref.
	↓	acetylation
	↑	H3K9 dimethylation	In-vitro	Liver, brain	Ke, 2006 [41]
Nickel	↑	H2A and H2B monoubiquitination
	↓	H4K12 acetylation	In-vitro	Yeast cells	Broday, 2000 [42]
	↓	H4K4 acetylation	In-vitro	Mammalian cells
	↑	H3K9 mono- and dimethylation	In-vitro	G12 cell line	Chen, 2006 [43]
	↓	Acetylation of histone H2B	In-vitro	HAE and NRK cell lines	Golebiowski, 2005 [45]
	↓↑	H2B ubiquitination	In-vitro	HAEo- and HPL1D cell lines	Karaczyn, 2006 [44]
Arsenic	↑	H3K9 dimethylation
	↓	H3K27 trimethylation	In-vitro	A549 cell line	Zhou, 2008 [87]
	↑	H3K4 trimethylation

^*Increase (+) or decrease (-) in histone modification