UASp sequences regulate expression of the coat protein of the MS2 RNA bacteriophage (Tag:MCP) fused to amino acids 1696-2239 of nej, in which the catalytic function of the nej histone acetyltransferase (HAT) domain has been abolished by introducing a F2161A amino acid substitution. The coding sequence is tagged with a nuclear localization signal and with 3xTag:FLAG.