. "\"Any process that activates or increases the frequency, rate or extent of the addition of an acetyl group to a histone protein.\" [GOC:bf]" . . "positive regulation of histone acetylation" . "up regulation of histone acetylation" . "up-regulation of histone acetylation" . "upregulation of histone acetylation" . . . . "activation of histone acetylation" . "stimulation of histone acetylation" .