Structural Analysis and Functional Identification of Nuclear Localization Signal Sequences in BRD7

Objective: To structurally analyse and functionally identify the nuclear localization signal(NLS) in BRD7 and then study its effect on the subcellular localization of BRD7. Methods: Bioinformatics was performed to predict and anslyse the nuclear localization signal sequences(NLSs) in BRD7, then green fluorescent protein(GFP) direct fluorescence and indirect immunofluorescence assays were used to identify the function of the NLSs and the effect on the subcellular localization of BRD7. Results: The region from amino acid 65 to 96 in BRD7 was characteristic of putative nuclear localization signal sequence and contained three clusters of base amino acid residues. It was viewed to consist of two bipartite nuclear targeting sequences, NLS1 and NLS2, which were tightly linked and extremely overlapped. It was also shown that both the entire NLS and the two bipartite nuclear targeting sequences, NLS1 and NLS2, could respectively determine the nuclear import of GFP, which supported that the region from aa 65 to 96 in BRD7 was a functional nuclear localization signal and the deletion of a cluster of base residues was insufficient to demolish the function of the NLS. The most important was that wild BRD7 localized in nucleus, whereas NLS-deleted BRD7 shifted the nuclear localization to be mostly in cytoplasm. Conclusion: The amino acid region from 65 to 96 is a functional NLS in BRD7 and it is an essential motif affecting BRD7 nuclear distribution.