J Biol Chem, Vol. 273, Issue 42, 27070-27075, October 16, 1998
The Phosphorylation of Protein S6 Modulates the Interaction of
the 40 S Ribosomal Subunit with the 5'-Untranslated Region of a
Dictyostelium Pre-spore-specific mRNA and Controls Its
Stability
Sara
Chiaberge,
Emanuele
Cassarino, and
Giorgio
Mangiarotti
From the Department of Clinical and Biological Sciences, University
of Turin, Ospedale S. Luigi, Orbassano (To), Italy 10043
AC914 mRNA, a pre-spore-specific mRNA
that accumulates only in the post-aggregation stage of development, is
transcribed constitutively as shown by nuclear run-off experiments and
by fusing its promoter to the luciferase reporter gene. The same
mRNA disappears quickly from disaggregated cells. If the
5'-untranslated region (5'UTR) of the constitutively expressed Actin 15 mRNA is substituted for the 5'UTR of AC914 mRNA, this can no
longer be destabilized and accumulates both in growing and
disaggregated cells. If the 5'UTR of AC914 mRNA is substituted for
the 5'UTR of Actin 15 mRNA, the latter accumulates only in
aggregated cells. Pactamycin, but not other inhibitors of protein
synthesis, prevents AC914 mRNA from being destabilized in
disaggregated cells, suggesting a role of 40 S subunits in the
destabilization. This has been confirmed by using an in
vitro system in which the in vivo stability of different mRNAs is reproduced. A protein kinase
A-dependent phosphorylation of ribosomal protein S6
determines whether 40 S subunits are capable or not of destabilizing
AC914 mRNA in the in vitro system.
Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc.