Nap1

NAP1 stands for Nucleosome Assembly Protein 1, a histone chaperone that facilitates the assembly and disassembly of nucleosomes by promoting the deposition of histone H2A–H2B dimers onto DNA and by preventing non-specific histone-DNA interactions. It helps maintain a supply of histones for chromatin and supports proper nucleosome formation during cellular processes.

NAP1 functions during DNA replication, repair, and transcription, contributing to chromatin dynamics and genome stability. It cooperates with other chromatin assembly factors, such as CAF-1 and the HIRA complex, and can participate in histone exchange. By regulating histone deposition and remodeling of nucleosomes, NAP1 influences access to DNA and the epigenetic state of chromatin.

In yeast, Nap1p is the archetype of the family. In higher eukaryotes, several NAP1-like proteins exist, including NAP1L1, NAP1L2, NAP1L3, and NAP1L4 in humans. These proteins share a conserved NAP1 domain and functional similarity with yeast Nap1, reflecting a broadly conserved role in histone management across species.

Structure and regulation: NAP1-family proteins are acidic and primarily cytosolic, shuttling to the nucleus as needed. They contain a conserved NAP domain and often form dimers or higher-order oligomers. Their activity is modulated by phosphorylation and interactions with histones and other chromatin factors, enabling responsive control of nucleosome assembly.

Clinical and research relevance: NAP1 contributes to genome stability through proper nucleosome assembly and chromatin maintenance. Misregulation has been linked to developmental processes and cancer in various models, making NAP1 and NAP1-like proteins important topics in chromatin biology and epigenetic regulation research.