The histone phosphatase inhibitory property of plant nucleosome assembly protein-related proteins (NRPs)

SET/I2PP2A, a member of the family of nucleosome assembly proteins (NAPs), has been previously described as a multifunctional protein inhibiting protein phosphatase 2A (PP2A)-mediated histone H3(pSer10) dephosphorylation during the heat shock response in animal cells. In the present work we demonstrate that its plant orthologs, designated as NAP-related proteins (NRPs), have a similar in vitro biochemical activity and interact with PP2A and histone H3(pSer10) in vivo. Although heat shock gene promoters were found to be associated with histone H3(pSer10)–marked chromatin following a high temperature treatment, heat shock gene expression was not affected in NRP-deficient mutant Arabidopsis thaliana (L.) plantlets. These observations indicate that NRPs are potential regulators of histone dephosphorylation in plants, but they are dispensable for gene expression reorganization in response to heat shock.