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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

Cellular & Molecular Biology Letters volume 18, pages 284–296 (2013)Cite this article

Abstract

The breast cancer type 1 susceptibility gene (BRCA1) is a tumor suppressor gene, mutations or loss of which lead to genomic instability and breast cancer. BRCA1 protein is part of a large multi-protein complex involved in a variety of DNA repair and transcription regulatory functions. At least four splice variants have been described and these differ in their function and tissue and spatio-temporal expression patterns. Structural analysis has revealed the presence of two nuclear localization signals (NLS) located in exon 11 of BRCA1. Interestingly, a splice variant of the protein that lacks both of the known NLS still manages to gain entry to the nucleus. While there is experimental proof for the translocation of these proteins by binding to other established nuclear proteins, we examined the possibility of a hitherto unidentified NLS in this particular variant. In this paper, we present evidence for the existence of a previously unreported non-canonical NLS contained within the first 39 amino acids of exon 11. A fusion protein with this 39mer and a reporter green fluorescent protein translocated into the nucleus when it was expressed in breast epithelial cells. We demonstrate the presence of a hitherto unreported noncanonical NLS in exon 11a of BRCA1. This NLS might aid proteins that were encoded by splice variants and lack the canonical NLS to localize to the nucleus.

Abbreviations

BARD1:

BRCA1-associated RING domain

BRCA1 :

breast cancer type 1 susceptibility protein

DAPI:

4′,6-diamidino-2-phenylindole

EGFP:

enhanced green fluorescent protein

GFP:

green fluorescent protein

HBL-100:

human breast carcinoma cell line

HEK-293:

human embryonic kidney 293 cells

NLS:

nuclear localization signals

Ubc9:

ubiquitin-conjugating enzyme 9

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Authors and Affiliations

  1. Division of Molecular Medicine, St. John’s Research Institute (SJRI), Bangalore, 560034, India

    Aruna Korlimarla, Lekhana Bhandary, Jyothi S. Prabhu, Hema Shankar, Hari Sankaranarayanan, Jose Remacle & T. S. Sridhar

  2. Prescient Biosciences Pvt.Ltd, Bangalore, India

    Pravin Kumar & Dipa Natarajan

Authors
  1. Aruna Korlimarla
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  2. Lekhana Bhandary
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  3. Jyothi S. Prabhu
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  4. Hema Shankar
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  5. Hari Sankaranarayanan
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  6. Pravin Kumar
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  7. Jose Remacle
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  9. T. S. Sridhar
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Correspondence to Aruna Korlimarla.

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These authors contributed equally to this manuscript

Visiting Scientist, SJRI

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Korlimarla, A., Bhandary, L., Prabhu, J.S. et al. Identification of a non-canonical nuclear localization signal (NLS) in BRCA1 that could mediate nuclear localization of splice variants lacking the classical NLS. Cell Mol Biol Lett 18, 284–296 (2013). https://doi.org/10.2478/s11658-013-0088-x

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Cellular & Molecular Biology Letters

ISSN: 1689-1392

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