J. Biol. Chem., Vol. 265, Issue 16, 9077-9082, Jun, 1990
cAMP stimulation of Dictyostelium discoideum destabilizes the mRNA for 117 antigen
MH Juliani, GM Souza and C Klein
Departmento de Bioquimica, Universidade de Sao Paulo, Brasil.
Transcription of the 117 gene and changes in its mRNA levels in
Dictyostelium discoideum were studied by mRNA hybridization with a cDNA
probe. In wild type cells (Ax-2), the expression is developmentally
regulated during cell aggregation, while in the aggregateless mutant, Agip
45, 117 mRNA is not detectable during cell starvation. Low concentrations
of cAMP, given in the form of extracellular pulses to induce the
development of starved Agip 45 cells to aggregation competence, are able to
induce the appearance of 117 mRNA. The induction seems to be via the cell
surface cAMP receptor and by a mechanism which does not involve changes in
intracellular cAMP. Interestingly, high concentrations of cAMP, which
down-regulate the cell surface cAMP receptor, elicit a rapid decrease in
the level of 117 mRNA in aggregation-competent cells. Nuclear run-off and
pulse-chase experiments show that the high concentrations of cAMP
selectively destabilize the mRNA for 117 antigen. This destabilization
requires both de novo mRNA synthesis and protein synthesis since the
addition of inhibitors of these processes eliminates the effects of cAMP on
117 mRNA. The data suggest that a cAMP-induced protein(s) may be involved
in the destabilization of selective mRNAs.