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Mol. Cell. Biol., 09 1996, 5015-5025, Vol 16, No. 9
M Wu, M Arsura, RE Bellas, MJ FitzGerald, H Lee, SL Schauer, DH Sherr and GE Sonenshein
Treatment of WEHI 231 immature B-lymphoma cells with an antibody against
their surface immunoglobulin (anti-Ig) induces apoptosis and has been
studied extensively as a model of B-cell tolerance. Anti-Ig treatment of
exponentially growing WEHI 231 cells results in an early transient increase
in c-myc expression that is followed by a decline to below basal levels;
this decrease in c-myc expression immediately precedes the induction of
cell death. Here we have modulated NF- kappaB/Rel factor activity, which
regulates the rate of c-myc gene transcription, to determine whether the
increase or decrease in c-Myc- levels mediates apoptosis in WEHI 231 cells.
Addition of the serine/threonine protease inhibitor N-tosyl-L-phenylalanine
chloromethyl ketone (TPCK), which blocks the normally rapid turnover of the
specific inhibitor of NF-kappaB/Rel IkappaBalpha in these cells, caused a
drop in Rel-related factor binding. TPCK treatment resulted in decreased
c-myc expression, preventing the usual increase seen following anti-Ig
treatment. Whereas inhibition of the induction of c- myc expression
mediated by anti-Ig failed to block apoptosis, reduction of c-myc
expression in exponentially growing WEHI 231 cells induced apoptosis even
in the absence of anti-Ig treatment. In WEHI 231 clones ectopically
expressing c-Myc, apoptosis induced by treatment with TPCK or anti-Ig was
significantly diminished and cells continued to proliferate. Furthermore,
apoptosis of WEHI 231 cells ensued following enhanced expression of Mad1,
which has been found to reduce functional c-Myc levels. These results
indicate that the decline in c-myc expression resulting from the drop in
NF-kappaB/Rel binding leads to activation of apoptosis of WEHI 231 B cells.
Copyright © 1996, American Society for Microbiology
Inhibition of c-myc expression induces apoptosis of WEHI 231 murine B cells
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118, USA.
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