Identification of a non-canonical nuclear localization signal (NLS) in BRCA1 that could mediate nuclear localization of splice variants lacking the classical NLS

Korlimarla, Aruna; Bhandary, Lekhana; Prabhu, Jyothi S; Shankar, Hema; Sankaranarayanan, Hari; Kumar, Pravin; Remacle, José; Natarajan, Dipa; Sridhar, T.S.

doi:10.2478/s11658-013-0088-x

Cited by 16 publications

(12 citation statements)

References 29 publications

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“…We first confirmed the cytoplasmic and nuclear expression of BRCA1 proteins (Figure S1A). As expected, full-length BRCA1 was entirely nuclear, while BRCA1-Δ11q that lacks an exon 11 located nuclear import signal was expressed similarly in both cytoplasmic and nuclear fractions (Chen et al, 1996; Korlimarla et al, 2013). The BRCA1-ΔBRCT and BRCA1-ΔCC+ΔBRCT proteins were detected in cytoplasm ic fractions but were predom inantly nuclear (Figure S1A).…”

Section: Resultssupporting

confidence: 76%

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance

et al. 2018

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SUMMARY BRCA1 functions in homologous recombination (HR) both up- and downstream of DNA end resection. However, in cells with 53BP1 gene knockout (KO), BRCA1 is dispensable for the initiation of resection, but whether BRCA1 activity is entirely redundant after end resection is unclear. Here, we found that 53bp1 KO rescued the embryonic viability of a Brea1ΔC/ΔC mouse model that harbors a stop codon in the coiled-coil domain. However, Brca1ΔC/ΔC;53bp1−/− mice were susceptible to tumor formation, lacked Rad51 foci, and were sensitive to PARP inhibitor (PARPi) treatment, indicative of suboptimal HR. Furthermore, BRCA1 mutant cancer cell lines were dependent on truncated BRCA1 proteins that retained the ability to interact with PALB2 for 53BP1 KO induced RAD51 foci and PARPi resistance. Our data suggest that the overall efficiency of 53BP1 loss of function induced HR may be BRCA1 mutation dependent. In the setting of 53BP1 KO, hypomorphic BRCA1 proteins are active downstream of end resection, promoting RAD51 loading and PARPi resistance.

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Section: Resultssupporting

confidence: 76%

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance

et al. 2018

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“…This suggests that NLS2 activity is dependent on determinants present in the first cluster of basic residues, in the sequence “RRDCGK”. Interestingly, this motif has similarities to that of a non-canonical NLS recently identified in a BRCA1 splice variant (KRAAER) [ 51 ], with two basic residues separated from a third basic residue by three amino acids.…”

Section: Discussionmentioning

confidence: 91%

Characterization of RanBPM Molecular Determinants that Control Its Subcellular Localization

2015

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RanBPM/RanBP9 is a ubiquitous, nucleocytoplasmic protein that is part of an evolutionary conserved E3 ubiquitin ligase complex whose function and targets in mammals are still unknown. RanBPM itself has been implicated in various cellular processes that involve both nuclear and cytoplasmic functions. However, to date, little is known about how RanBPM subcellular localization is regulated. We have conducted a systematic analysis of RanBPM regions that control its subcellular localization using RanBPM shRNA cells to examine ectopic RanBPM mutant subcellular localization without interference from the endogenously expressed protein. We show that several domains and motifs regulate RanBPM nuclear and cytoplasmic localization. In particular, RanBPM comprises two motifs that can confer nuclear localization, one proline/glutamine-rich motif in the extreme N-terminus which has a dominant effect on RanBPM localization, and a second motif in the C-terminus which minimally contributes to RanBPM nuclear targeting. We also identified a nuclear export signal (NES) which mutation prevented RanBPM accumulation in the cytoplasm. Likewise, deletion of the central RanBPM conserved domains (SPRY and LisH/CTLH) resulted in the relocalization of RanBPM to the nucleus, suggesting that RanBPM cytoplasmic localization is also conferred by protein-protein interactions that promote its cytoplasmic retention. Indeed we found that in the cytoplasm, RanBPM partially colocalizes with microtubules and associates with α-tubulin. Finally, in the nucleus, a significant fraction of RanBPM is associated with chromatin. Altogether, these analyses reveal that RanBPM subcellular localization results from the combined effects of several elements that either confer direct transport through the nucleocytoplasmic transport machinery or regulate it indirectly, likely through interactions with other proteins and by intramolecular folding.

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“…NLSs are categorized into cNLSs and non-classical NLSs (ncNLS) ( 40 ). cNLSs are characterized by either monopartite (e.g., PKKKRRV from SV40 large T antigen) or bipartite (e.g., KRPAATKKAGQAKKKK from nucleoplasmin) stretches of basic amino acids ( 41 , 42 ).…”

Section: Discussionmentioning

confidence: 99%

Nuclear import of prototype foamy virus transactivator Bel1 is mediated by KPNA1, KPNA6 and KPNA7

Duan

Tang

Hong

et al. 2016

International Journal of Molecular Medicine

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Bel1, a transactivator of the prototype foamy virus (PFV), plays pivotal roles in the replication of PFV. Previous studies have demonstrated that Bel1 bears a nuclear localization signal (NLS); however, its amino acid sequence remains unclear and the corresponding adaptor importins have not yet been identified. In this study, we inserted various fragments of Bel1 into an EGFP-GST fusion protein and investigated their subcellular localization by fluorescence microscopy. We found that the 215PRQKRPR221 fragment, which accords with the consensus sequence K(K/R)X(K/R) of the monopartite NLS, directed the nuclear translocation of Bel1. Point mutation experiments revealed that K218, R219 and R221 were essential for the nuclear localization of Bel1. The results of GST pull-down assay revealed that the Bel1 peptide 215-221, which bears the NLS, interacted with the nucleocytoplasmic transport receptors, karyopherin alpha 1 (importin alpha 5) (KPNA1), karyopherin alpha 6 (importin alpha 7) (KPNA6) and karyopherin alpha 7 (importin alpha 8) (KPNA7). Finally, in vitro nuclear import assays demonstrated that KPNA1, KPNA6 or KPNA7, along with other necessary nuclear factors, caused Bel1 to localize to the nucleus. Thus, the findings of our study indicate that KPNA1, KPNA6 and KPNA7 are involved in Bel1 nuclear distribution.

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Identification of a non-canonical nuclear localization signal (NLS) in BRCA1 that could mediate nuclear localization of splice variants lacking the classical NLS

Cited by 16 publications

References 29 publications

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance

Characterization of RanBPM Molecular Determinants that Control Its Subcellular Localization

Nuclear import of prototype foamy virus transactivator Bel1 is mediated by KPNA1, KPNA6 and KPNA7

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