title: YB-1 disrupts mismatch repair complex formation, interferes with MutSα recruitment on mismatch and inhibits mismatch repair through interacting with PCNA.
abstract: Y-box binding protein-1 (YB-1) is highly expressed in tumors and it participates in various cellular processes. Previous studies indicated that YB-1 binds to mispaired DNA and interacts with several mismatch repair (MMR)-related factors. However, its role in the MMR system remains undefined. Here, we found that YB-1 represses mutS homolog 6 (MSH6)-containing MMR complex formation and reduces MutSα mismatch binding activity by disrupting interactions among MMR-related factors. In an effort to elucidate how YB-1 exerts this inhibitory effect, we have identified two functional proliferating cell nuclear antigen (PCNA)-interacting protein (PIP)-boxes that mediate YB-1/PCNA interaction and locate within the C-terminal region of YB-1. This interaction is critical for the regulatory role of YB-1 in repressing MutSα mismatch binding activity, disrupting MutSα/PCNA/G/T heteroduplex ternary complex formation and inhibiting in vitro MMR activity. The differential regulation of 3' and 5' nick-directed MMR activity by YB-1 was also observed. Moreover, YB-1 overexpression is associated with the alteration of microsatellite pattern and the enhancement of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced and spontaneous mutations. Furthermore, upregulation of other PIP-box-containing proteins, such as myeloid cell leukemia-1 (Mcl-1) and inhibitor of growth protein 1b (ING1b), has no impact on MMR complex formation and mutation accumulation, thus revealing the significant effect of YB-1 on regulating the MMR system. In conclusion, our study suggests that YB-1 functions as a PCNA-interacting factor to exert its regulatory role on the MMR process and involves in the induction of genome instability, which may partially account for the oncogenic potential of YB-1.
authors.affiliation: Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Y-W
authors.initials: YW
authors.lastname: Chang
authors.affiliation: 1] Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan [2] Department of Biological Science and Technology, College of Biological Science and Technology, National Chiao-Tung University, Hsinchu, Taiwan.
authors.forename: R-T
authors.initials: RT
authors.lastname: Mai
authors.affiliation: Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: W-H
authors.initials: WH
authors.lastname: Fang
authors.affiliation: Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: C-C
authors.initials: CC
authors.lastname: Lin
authors.affiliation: Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: C-C
authors.initials: CC
authors.lastname: Chiu
authors.affiliation: 1] Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan [2] Department of Biological Science and Technology, College of Biological Science and Technology, National Chiao-Tung University, Hsinchu, Taiwan.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Wu Lee
mesh_terms: D001665:Binding Sites; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D053842:Microsatellite Instability; D051718:MutS Homolog 2 Protein / Q000378:metabolism*; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D051840:Y-Box-Binding Protein 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D018809:Proliferating Cell Nuclear Antigen; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D008769:Methylnitronitrosoguanidine; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein