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Mol. Cell. Biol., Sep 1996, 4754-4764, Vol 16, No. 9
RM Jones, J Branda, KA Johnston, M Polymenis, M Gadd, A Rustgi, L Callanan and EV Schmidt
The mRNA cap-binding protein (eukaryotic initiation factor 4E [eIF4E])
binds the m7 GpppN cap on mRNA, thereby initiating translation. eIF4E is
essential and rate limiting for protein synthesis. Overexpression of eIF4E
transforms cells, and mutations in eIF4E arrest cells in G, in cdc33
mutants. In this work, we identified the promoter region of the gene
encoding eIF4E, because we previously identified eIF4E as a potential
myc-regulated gene. In support of our previous data, a minimal, functional,
403-nucleotide promoter region of eIF4E was found to contain CACGTG E box
repeats, and this core eIF4E promoter was myc responsive in cotransfections
with c-myc. A direct role for myc in activating the eIF4E promoter was
demonstrated by cotransfections with two dominant negative mutants of c-myc
(MycdeltaTAD and MycdeltaBR) which equally suppressed promoter function.
Furthermore, electrophoretic mobility shift assays demonstrated
quantitative binding to the E box motifs that correlated with myc levels in
the electrophoretic mobility shift assay extracts; supershift assays
demonstrated max and USF binding to the same motif. cis mutations in the
core or flank of the eIF4E E box simultaneously altered myc-max and USF
binding and inactivated the promoter. Indeed, mutations of this E box
inactivated the promoter in all cells tested, suggesting it is essential
for expression of eIF4E. Furthermore, the GGCCACGTG(A/T)C(C/G) sequence is
shared with other in vivo targets for c-myc, but unlike other targets, it
is located in the immediate promoter region. Its critical function in the
eIF4E promoter coupled with the known functional significance of eIF4E in
growth regulation makes it a particularly interesting target for c-myc
regulation.
Copyright © 1996, American Society for Microbiology
An essential E box in the promoter of the gene encoding the mRNA cap- binding protein (eukaryotic initiation factor 4E) is a target for activation by c-myc
Massachusetts General Hospital Cancer Center, Charlestown, 02129, USA.
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