Overexpression of nucleolin in chronic lymphocytic leukemia cells induces stabilization of bcl2 mRNA.
B-cell chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells that are resistant to apoptosis as a result of bcl2 oncogene overexpression. Studies were done to determine the mechanism for the up-regulation of bcl-2 protein observed in CD19+ CLL cells compared with CD19+ B cells from healthy volunteers. The 11-fold higher level of bcl-2 protein in CLL cells was positively correlated with a 26-fold elevation in the cytosolic level of nucleolin, a bcl2 mRNA-stabilizing protein. Measurements of the bcl2 heterogeneous nuclear/bcl2 mRNA (hnRNA)/mRNA ratios and the rates of bcl2 mRNA decay in cell extracts indicated that the 3-fold higher steady-state level of bcl2 mRNA in CLL cells was the result of increased bcl2 mRNA stability. Nucleolin was present throughout the nucleus and cytoplasm of CLL cells, whereas in normal B cells nucleolin was only detected in the nucleus. The addition of recombinant human nucleolin to extracts of normal B cells markedly slowed the rate of bcl2 mRNA decay. SiRNA knockdown of nucleolin in MCF-7 cells resulted in decreased levels of bcl2mRNA and protein but no change in beta-actin. These results indicate that bcl-2 overexpression in CLL cells is related to stabilization of bcl2 mRNA by nucleolin.
Otake
Yoko
Y
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
Soundararajan
Sridharan
S
Sengupta
Tapas K
TK
Kio
Ebenezer A
EA
Smith
James C
JC
Pineda-Roman
Mauricio
M
Stuart
Robert K
RK
Spicer
Eleanor K
EK
Fernandes
Daniel J
DJ
D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D019254:Genes, bcl-2; D006801:Humans; D066298:In Vitro Techniques; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D000097796:Nucleolin
D010750:Phosphoproteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000097796:Nucleolin