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Amplification of the metallothionein‐1 and metallothionein‐2 genes in copper‐resistant hepatoma cells
Author(s) -
Czaja Mark J.,
Weiner Francis R.,
Freedman Jonathan H.
Publication year - 1991
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041470308
Subject(s) - metallothionein , microbiology and biotechnology , messenger rna , gene expression , northern blot , gene , cell culture , biology , transcription (linguistics) , western blot , copper , chemistry , biochemistry , genetics , linguistics , philosophy , organic chemistry
The molecular basis for increased metallothionein concentrations in copperresistant hepatoma cells was examined. The copper‐resistant cell line HAC 600 , which is maintained in 600 μm copper, had increased steady‐state mRNA levels for both the metallothionein‐1 (MT‐1) and the metallothionein‐2 (MT‐2) genes. Levels of mRNA were increased 11‐fold for MT‐1 and 15‐fold for MT‐2, with no significant change in α‐tubulin mRNA content. HAC 600 NM cells, which are copper‐resistant cells kept in a normal copper concentration for over 1 year, also had eight‐ and tenfold increases in MT‐1 and MT‐2 mRNA levels. Nuclear run‐on assays showed that MT‐1 and MT‐2 gene transcription was increased nine‐ and eightfold in HAC 600 cells and seven‐ and tenfold in HAC 600 NM cells, respectively. Southern blot analysis showed amplification of both metallothionein genes in HAC 600 and HAC 600 NM cells. Thus the molecular basis of increased metallothionein in these hepatoma cells involved a stable gene amplification of both MT genes. The greater increase in metallothionein mRNA levels in HAC 600 cells relative to the changes in transcription suggests that posttranscriptional mechanisms of gene regulation may also be acting in these cells.