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Detection of Heterodimerization of Protein Isoforms Using an in Situ Proximity Ligation Assay
Published on: October 20, 2018
Heterodimerization with LBP-1b is necessary for nuclear localization of LBP-1a and LBP-1c
Fuyuhiko Sato1, Ken-ichi Yasumoto, Kota Kimura
1Department of Biomolecular Science, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.
Abstract:
The LBP-1 family consists of four proteins, which act as transcription factors in the formation of dimers with a member of this family. LBP-1a and LBP-1b are splicing variants from one gene, and LBP-1c and LBP-1d also arise from the alternative splicing of another gene. Investigation of subcellular localization of LBP-1 proteins fused to YFP revealed that the LBP-1b was localized in the nucleus, whereas LBP-1a and LBP-1c were exclusively localized in the cytosol. The peptide of 36 amino acids encoded by exon 6, a specific exon used only for LBP-1b, possessed the function of a nuclear localization signal (NLS). Nuclear localization of LBP-1a and LBP-1c occurred when LBP-1b was co-expressed, suggesting that heterodimerization of LBP-1a and LBP-1c with LBP-1b is important for their nuclear transport. Transiently expressed LBP-1 proteins in COS-7 cells formed speckles in the nucleus. Most speckles overlapped with the PML body. The activity of LBP-1a for accumulation in the PML body was mapped in the N-terminal region.
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