TY - JOUR
T1 - Relationship of c‐myc gene copy number and gene expression
T2 - Cellular effects of elevated c‐myc protein
AU - Pallavicini, M. G.
AU - Rosette, C.
AU - Reitsma, M.
AU - Deteresa, P. S.
AU - Gray, J. W.
PY - 1990/5
Y1 - 1990/5
N2 - The relationship between gene copy number and expression and cellular consequences of elevated levels of c‐myc protein has been investigated using recombinant Chinese hamster ovary cell lines transfected with DNA coding for the murine c‐myc gene. HC‐8 and LC‐5 recombinant cells carry approximately 800 and 50 copies of c‐myc sequences, respectively, under control of an inducible heat shock promoter. Multivariate flow cytometric analysis and clonogenic assays were used to measure the relationship among c‐myc expression, rate of DNA synthesis, and cell survival. Following heat exposure, maximally induced HC‐8 cells produced approximately tenfold more c‐myc protein than heated LC‐5 cells, suggesting a close relationship between gene copy number and level of expression. However, considerable heterogeneity in the level and time of c‐myc expression was observed following heat induction, even though the amounts of genomic c‐myc were reatively constant. Heterogeneity in gene expression was not attributable to variation in heat induction methodologies and/or cell cycle phase distributions. The presence of high levels of recombinant c‐myc protein was associated with a decreased rate of bromodeoxyuridine incorporation into DNA. High levels of c‐myc protein in HC‐8 cells were inversely correlated with cell survival postheating, suggesting that high levels of c‐myc protein are incompatible with cell survival.
AB - The relationship between gene copy number and expression and cellular consequences of elevated levels of c‐myc protein has been investigated using recombinant Chinese hamster ovary cell lines transfected with DNA coding for the murine c‐myc gene. HC‐8 and LC‐5 recombinant cells carry approximately 800 and 50 copies of c‐myc sequences, respectively, under control of an inducible heat shock promoter. Multivariate flow cytometric analysis and clonogenic assays were used to measure the relationship among c‐myc expression, rate of DNA synthesis, and cell survival. Following heat exposure, maximally induced HC‐8 cells produced approximately tenfold more c‐myc protein than heated LC‐5 cells, suggesting a close relationship between gene copy number and level of expression. However, considerable heterogeneity in the level and time of c‐myc expression was observed following heat induction, even though the amounts of genomic c‐myc were reatively constant. Heterogeneity in gene expression was not attributable to variation in heat induction methodologies and/or cell cycle phase distributions. The presence of high levels of recombinant c‐myc protein was associated with a decreased rate of bromodeoxyuridine incorporation into DNA. High levels of c‐myc protein in HC‐8 cells were inversely correlated with cell survival postheating, suggesting that high levels of c‐myc protein are incompatible with cell survival.
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U2 - 10.1002/jcp.1041430223
DO - 10.1002/jcp.1041430223
M3 - Article
C2 - 2185254
AN - SCOPUS:0025275370
SN - 0021-9541
VL - 143
SP - 372
EP - 380
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
IS - 2
ER -