Cell cycle analysis of p26-BCL-2 protein levels in proliferating lymphoma and leukemia cell lines.
The BCL-2 (B-cell lymphoma/leukemia-2) gene is frequently involved in t(14;18) translocations in non-Hodgkin's lymphomas and encodes a 26-kDa intracellular, membrane-associated protein. Expression of the BCL-2 gene has previously been correlated with cellular proliferation in normal and neoplastic lymphoid cells under a variety of experimental conditions. To examine the regulation of p26-BCL-2 protein levels during the cell cycle, we utilized the method of counterflow centrifugal elutriation to enrich for cells in various phases of the cell cycle. Relative levels of p26-BCL-2 protein were measured by immunoblotting, and comparisons were made with a cell cycle-regulated protein, p62-CYCLIN-A, and a protein whose levels are constant throughout the cell cycle, p36-PCNA (DNA polymerase-delta auxiliary factor). Relative levels of p26-BCL-2 and p36-PCNA did not vary among cell fractions enriched for specific phases of the cell cycle, whereas p62-CYCLIN-A was elevated in late S- and G2/M-phase cells. Similar results were obtained with lymphoma and leukemia cell lines that have either normal or translocated BCL-2 genes. These results obtained by elutriation were confirmed by pharmacologically inducing cell cycle arrest in proliferating lymphoid cell lines with hydroxyurea, quercetin, and nocodazole which blocked cells at S, G2, and M phases, respectively. Taken together, the data indicate that p26-BCL-2 is not a true cell cycle-regulated protein, although its levels can fluctuate in connection with changes in rates of cellular proliferation under some circumstances.
Reed
J C
JC
University of Pennsylvania, Department of Pathology and Laboratory Medicine, Philadelphia 19104-6082.
Tanaka
S
S
Cuddy
M
M
D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002498:Centrifugation / Q000379:methods; D015973:Gene Expression Regulation, Leukemic / Q000235:genetics / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D015321:Gene Rearrangement / Q000235:genetics; D007942:Leukemia, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D014407:Tumor Cells, Cultured
D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2