Complex Regulation of c-myc Gene Expression in a Murine B Cell Lymphoma
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Alterations in the structure of the c-myc gene have implicated this oncogene in many types of B cell neoplasias. Changes include chromosomal translocation to an immunoglobulin gene locus, retroviral insertion into the c-myc promoter, and gene amplification. While in most cases the change in c-myc gene structure leaves the protein product unaffected, the regulation of expression of the gene may be altered. In many cell systems, e.g. splenic lymphocytes, untransformed fibroblast lines, and rat liver (Kelly et. al., 1983, Campisi et al., 1984, Goyette et. al., 1984), expression of c-myc mRNA is low in quiescence and increases rapidly upon exit from the GO state. Quiescent B lymphocytes contain barely detectable levels of c-myc mRNA. Upon stimulation with the mitogen LPS, c-myc mRNA levels increase 20 to 30 fold within 2–3 hours (Kelly et al., 1983). Terminal differentiation is accompanied by a decrease in expression of c-myc mRNA (Campisi et al., 1984, Grosso and Pitot 1985, Lachman and Skoultchi, 1984). These results suggest a role for the c-myc gene in the control of proliferation and differentiation. Since maturation of B cells involves several stages of differentiation, including terminal differentiation to nonproliferating plasma cells, it seemed likely that alterations in c-myc gene regulation might lead to aberrant B cell growth and differentiation.
KeywordsDaudi Cell Aberrant Transcript Cytoplasmic mRNA Message Stability Sense Strand Transcription
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