The strand separation and nuclease activities associated with YB-1 are dispensable for cisplatin resistance but overexpression of YB-1 in MCF7 and MDA-MB-231 breast tumor cells generates several chemoresistance signatures.
YB-1 is a protein involved in DNA repair, transcription, splicing, translation, and confers cisplatin resistance in several cancers. However, it is unknown which YB-1 activity is required for this resistance. To identify the mechanism(s) by which nuclear YB-1 confers cisplatin resistance, we generated several YB-1 mutants and tested their impact on resistance in the mammary tumor cell lines MCF7 and MDA-MB-231. Transfection of wild type YB-1 bestowed cisplatin resistance in such cells but a mutant YB-1 with a point mutation at position 175 (YB-1(E175A)) did not. A truncated YB-1(1-205) increased cisplatin resistance above the levels conferred by wild type YB-1. The truncated YB-1(1-205) has intact nuclease activities but could not separate a DNA duplex containing a Y-box sequence (activities associated with DNA repair). Moreover, this truncated YB-1(1-205) did not alter splicing of the adenovirus E1A pre-mRNA minigene as it had low binding affinity for several splicing factors. In contrast, the mutant YB-1(E175A) protein behaved like wild type YB-1 regarding all these activities but yet did not confer cisplatin resistance. Finally, transfection of mutant YB-1(E175A) had low impact on overall transcription. The wild type and truncated YB-1(1-205) induced important but different alterations in gene expression as revealed by microarray analyses. Our results indicate that the splicing and the nuclease activities associated with YB-1 have minor impact on cisplatin resistance. In contrast, the global expression profiles displayed by both wild type and truncated YB-1(1-205) revealed several chemoresistance signatures which differed depending on the genetic status of the breast cancer cell line used.
Centre de Recherche en Cancérologie de l'Université Laval, Hôpital Hôtel-Dieu de Québec, 9 McMahon Street, Québec G1R 2J6, Canada.
David
D
Guay
Audrey-Ann
AA
Evoy
Eric
E
Paquet
Chantal
C
Garand
Magdalena
M
Bachvarova
Dimcho
D
Bachvarov
Michel
M
Lebel
D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000627:therapeutic use*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D009944:Organoplatinum Compounds / Q000627:therapeutic use; D000077150:Oxaliplatin; D017354:Point Mutation; D012326:RNA Splicing; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051840:Y-Box-Binding Protein 1
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009944:Organoplatinum Compounds; D016159:Tumor Suppressor Protein p53; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D000077150:Oxaliplatin; D002945:Cisplatin