Study : NRP histone chaperones promote the removal of histone variant H2A.Z


NRP histone chaperones promote the removal of histone variant H2A.Z
In eukaryotes, DNA wraps around histones to form nucleosomes, which are compacted into chromatin. DNA-templated processes, including transcription, require chromatin disassembly and reassembly mediated by histone chaperones. Additionally, distinct histone variants can replace core histones to regulate chromatin structure and function. Although replacement of H2A with the evolutionarily conserved H2A.Z via the SWR1 histone chaperone complex has been extensively studied, in plants little is known about how a reduction of H2A.Z levels can be achieved in plants. Here, we show that NRP proteins cause a decrease of H2A.Z-containing nucleosomes in Arabidopsis under standard growing conditions. nrp1-1 nrp2-2 double mutants show an over-accumulation of H2A.Z genome-wide, especially at heterochromatic regions normally H2A.Z-depleted in wild-type plants. Our work suggests that NRP proteins regulate gene expression by counteracting SWR1, thereby preventing excessive accumulation of H2A.Z. Overall design: In Arabidopsis, NRP proteins have been implicated in several biological processes, including cell-cycle control, root meristem formation, heat tolerance, DNA repair, somatic homologous recombination, and genome defense under genotoxic stress. NRP proteins are localized mainly in the nucleus and bind H2A, H2B, H3, and H4 histones. However, a molecular mechanism for these proteins has not been clearly established.


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