Nucleosome assembly protein 1-like 1

NAP1L1 (Nucleosome assembly protein 1-like 1) is a histone chaperone that facilitates the nuclear import and assembly of H2A-H2B dimers into nucleosomes (UniProt: P55209). Beyond chromatin assembly, it enhances ERCC6-mediated transcription-coupled nucleotide excision repair and stimulates homologous recombination by RAD51 and RAD54 in double-strand break repair. The protein also regulates embryonic neurogenesis by promoting neural progenitor proliferation and inhibiting neuronal differentiation through modulation of RASSF10 and H3K4 methylation.

NAP1L1 is expressed across tissues with particular developmental relevance in the central nervous system during cortical development. The protein has been implicated in viral reactivation and assembly processes during herpesvirus infections. No Mendelian disease associations are documented in UniProt.

In Alzheimer's disease, NAP1L1 is significantly downregulated in post-mortem AD brain tissue compared to age-matched controls (mean log2 fold-change: −0.42; Chaparral AD proteomics). This reduction was observed in human post-mortem AD brain tissue analyzed via TMT-labeled quantitative proteomics across subcellular fractions, suggesting a potential loss of nucleosome assembly capacity and DNA repair function in the AD brain.