Regulation Of Messenger Rna Stability And The Poly(A) Problem In Dictyostelium-Discoideum

This paper reviews our studies of three aspects of post‐transcriptional regulation in Dictyostelium discoideum: (1) the determinants of mRNA stability in vegetative amoebae; (2) the effects of disaggregation and cyclic AMP on the decay rates of cell‐type‐specific mRNAs in late developing cells; and (3) the cytoplasmic function of the 3′ poly(A) tracts present on most mRNAs. We find that: (1) mRNA stability in vegetative amoebae is not dependent on mRNA size, ribosome loading, or poly(A) tract length, but may be determined by specific 3′‐untranslated sequences within a given mRNA; (2) mRNA decay rates in late developing cells are heterogeneous, and cyclic AMP does not act directly to stabilize cell‐type‐specific mRNAs; and (3) poly(A) is most likely involved in the initiation of protein synthesis via an interaction with cytoplasmic poly(A)‐binding proteins.