Constitutive versus cell cycle regulation of c-myb mRNA expression correlates with developmental stages in murine B lymphoid tumors.
The expression of c-myb mRNA is differentially regulated in murine B lymphoid tumors such that B cell lymphomas and plasmacytomas contain significantly less c-myb mRNA than pre-B cell lymphomas. To examine the low level of c-myb mRNA expression in the murine B cell lymphoma cell line BCL1, nonessential amino acid starvation was used to block these cells in a G1 state. When BCL1 cells were released from this block, a 7- to 10-fold increase in c-myb mRNA was detected in late G1 and S phase cells relative to that detected in exponentially growing BCL1 cells. This increase was not inhibited by aphidicolin. To determine whether cell cycle regulation of c-myb mRNA expression occurred during exponential growth in both murine pre-B cell lymphoma and B cell lymphoma cell lines, elutriation was used to separate exponentially growing cell populations. An increase in c-myb mRNA expression was seen in late G1 and S phase fractions from B cell lymphoma cell lines. In contrast, c-myb mRNA levels remained constant in elutriation fractions isolated from pre-B cell lymphoma cell lines. Expression of c-myb mRNA was not detected in exponentially growing or in Go serum-stimulated murine fibroblasts. These results indicate that constitutive vs cell cycle regulation of c-myb mRNA expression is related to the state of differentiation in murine B lymphoid tumors and suggest that a switch in regulation may occur during normal B cell development.
Catron
K M
KM
Department of Microbiology, School of Medicine, University of Virginia, Charlottesville 22908.
Purkerson
J M
JM
Isakson
P C
PC
Bender
T P
TP
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D002453:Cell Cycle; D002469:Cell Separation; D015972:Gene Expression Regulation, Neoplastic; D005796:Genes; D016259:Genes, myc; D006657:Histones / Q000235:genetics; D015448:Leukemia, B-Cell / Q000235:genetics*; D016393:Lymphoma, B-Cell / Q000235:genetics*; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D020598:Proto-Oncogene Proteins c-myb; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D006657:Histones; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D020598:Proto-Oncogene Proteins c-myb; D012333:RNA, Messenger; D012334:RNA, Neoplasm