Binds to the genomic viral ssDNA, shuttles it into and out of the cell nucleus. Begomoviruses use 2 proteins to transport their DNA from cell to cell. The nuclear shuttle protein (NSP) shuttles it between nucleus and cytoplasm and the movement protein (MP) probably transports the DNA-NSP complex to the cell periphery and facilitates movement across the cell wall (By similarity). Binds to single-stranded and double-stranded viral DNA. Interacts with the host nuclear shuttle interacting (NSI) protein. This interaction may allow NSP to recruit NSI monomers to the viral genome and thus regulate nuclear export of viral genome by NSP. Translocated to the plasma membrane by the movement protein BC1. Belongs to the begomovirus nuclear shuttle protein family.