Intracellular localization and content of YB-1 protein in multidrug resistant tumor cells.
The multifunctional mammalian protein YB-1 is a member of the large DNA- and RNA-binding protein family with an evolutionarily ancient cold-shock domain. YB-1 is involved in multiple DNA- and mRNA-dependent events and regulates gene expression at various levels. It can be found both in the nucleus and the cytoplasm. Bound to DNA in the cell nucleus, YB-1 functions as a transcription factor interacting with inverted CCAAT-box (Y-box) in promoters and enhancers of multiple genes. In particular, YB-1 regulates activity of the multidrug resistance (MDR) genes MDR1 and LRP. In tumors, YB-1 has been suggested to be an early and global marker of MDR. In this study, we compared amounts of YB-1 mRNAs and intracellular localization of YB-1 protein in six pairs of drug sensitive and drug resistant sublines of diverse tumors. We have shown that neither great increase in the level of YB-1 mRNA nor substantial increase in the number of cells with nuclear localization of YB-1 are obligatory traits of drug resistant tumor cell populations. However, the cells with highest amounts of YB-1 mRNA also demonstrated increased quantities of MDR1, MRP1, BCRP, and LRP mRNAs encoding different MDR proteins. Transfection of two different populations of drug-sensitive cells with YB-1 cDNA led to increase in the amount of YB-1 mRNA. The quantities of MRP1 and LRP mRNAs increased in both populations. Introduction of YB-1 small hairpin RNA (shRNA) resulted in decreased amounts of YB-1 mRNA, as well as MRP1, LRP, and MDR1 mRNAs (in three different cell lines). Our data suggest that although YB-1 regulates several MDR genes, it could not be regarded as a global marker of already formed drug resistant tumor cell populations. It is most likely that at the first steps of MDR development YB-1 activity is necessary for propagation of resistant cell populations rather than for maintenance of drug resistance.
Institute of Carcinogenesis, Blokhin Russian Cancer Research Center, Russian Academy of Medical Sciences, 115478 Moscow, Russia. vaiman@yandex.ru
A V
AV
Vaiman
T P
TP
Stromskaya
E Yu
EY
Rybalkina
A V
AV
Sorokin
S G
SG
Guryanov
T N
TN
Zabotina
E B
EB
Mechetner
L P
LP
Ovchinnikov
A A
AA
Stavrovskaya
D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D045325:HCT116 Cells; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism*; D020014:K562 Cells; D007624:KB Cells; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D034622:RNA Interference; D012320:RNA Polymerase III / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics; D020394:Vault Ribonucleoprotein Particles / Q000096:biosynthesis / Q000235:genetics; D051840:Y-Box-Binding Protein 1; D000099187:Major Vault Protein
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D012320:RNA Polymerase III; D012333:RNA, Messenger; D012367:RNA, Viral; D020394:Vault Ribonucleoprotein Particles; D051840:Y-Box-Binding Protein 1; D000099187:Major Vault Protein; C070856:YBX1 protein, human; C421109:multidrug resistance-associated protein 1