Schematic representation of various domains of the NP. Numbers indicate amino acid positions. nNLS: non-conventional nuclear localization signal; cNLS: classical nuclear localization signal; NAS/CRS: nuclear accumulation signal/cytoplasmic retention signal; obpNLS: overlapping bipartite nuclear localization signal; bpNLS: bipartite nuclear localization signal. Critical amino acids contributing to a bpNLS motif are represented by two basic aa-rich domains (in bold) and the spacer 10 aa are underlined. Also note that the cNLS contains a slightly longer (12 aa) spacer region and thereby does not strictly qualify as a classical bpNLS by the PSORT program.