Karyopherin α-2 Mediates MDC1 Nuclear Import through a Functional Nuclear Localization Signal in the tBRCT Domain of MDC1.

Abstract

Mediator of DNA damage checkpoint protein 1 (MDC1) plays a vital role in DNA damage response (DDR) by coordinating the repair of double strand breaks (DSBs). Here, we identified a novel interaction between MDC1 and karyopherin α-2 (KPNA2), a nucleocytoplasmic transport adaptor, and showed that KPNA2 is necessary for MDC1 nuclear import. Thereafter, we identified a functional nuclear localization signal (NLS) between amino acid residues 1989-1994 of the two Breast Cancer 1 (BRCA1) carboxyl-terminal (tBRCT) domain of MDC1 and demonstrated disruption of this NLS impaired interaction between MDC1 and KPNA2 and reduced nuclear localization of MDC1. In KPNA2-depleted cells, the recruitment of MDC1, along with the downstream signaling p roteins Ring Finger Protein 8 (RNF8), 53BP1-binding protein 1 (53BP1), BRCA1, and Ring Finger Protein 168 (RNF168), to DNA damage sites was abolished. Additionally, KPNA2-depleted cells had a decreased rate of homologous recombination (HR) repair. Our data suggest that KPNA2-mediated MDC1 nuclear import is important for DDR signaling and DSB repair.

• Authors: Kamalakannan Radhakrishnan, Seon-Joo Park, Seok Won Kim, Gurusamy Hariharasudhan, Seo-Yeon Jeong, In Youb Chang, Jung-Hee Lee
• Journal: International journal of molecular sciences (Int J Mol Sci) Vol. 21 Issue 7 (Apr 10 2020) ISSN: 1422-0067 [Electronic] Switzerland
• PMID: 32290222 (Publication Type: Journal Article)

Chemical References

• Adaptor Proteins, Signal Transducing
• Cell Cycle Proteins
• MDC1 protein, human
• Nuclear Localization Signals
• alpha Karyopherins
• karyopherin alpha 2

Topics

• Active Transport, Cell Nucleus
• Adaptor Proteins, Signal Transducing (chemistry, metabolism)
• Cell Cycle Proteins (chemistry, metabolism)
• Cell Line, Tumor
• DNA Damage
• Gene Knockdown Techniques
• Humans
• Nuclear Localization Signals
• Protein Binding
• Protein Interaction Domains and Motifs
• Recombinational DNA Repair
• alpha Karyopherins (genetics, metabolism)