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QuickView for NAP-like superfamily (biogroup)
- Description:
- It is thought that NAPs act as histone chaperones, shuttling both core and linker histones from their site of synthesis in the cytoplasm to the nucleus. The proteins may be involved in regulating gene expression and therefore cellular differentiation. The centrosomal protein c-Nap1, also known as Cep250, has been implicated in the cell-cycle-regulated cohesion of microtubule-organizing centres. This 281 kDa protein consists mainly of domains predicted to form coiled coil structures. The C-terminal region defines a novel histone-binding domain that is responsible for targeting CNAP1, and possibly condensin, to mitotic chromosomes. During interphase, C-Nap1 localizes to the proximal ends of both parental centrioles, but it dissociates from these structures at the onset of mitosis. Re-association with centrioles then occurs in late telophase or at the very beginning of G1 phase, when daughter cells are still connected by post-mitotic bridges. Electron microscopic studies performed on isolated centrosomes suggest that a proteinaceous linker connects parental centrioles and C-Nap1 may be part of a linker structure that assures the cohesion of duplicated centrosomes during interphase, but that is dismantled upon centrosome separation at the onset of mitosis. The structure of NAP-1 has a long alpha-helix, responsible for homodimerization via a previously uncharacterized antiparallel non-coiled-coil, and an alpha/beta domain composed of four-stranded antiparallel beta-sheet, implicated in protein-protein interaction.
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