Conservation of Bmp2 post-transcriptional regulatory mechanisms

Bone morphogenetic protein (BMP) orthologs from diverse species like flies and humans are functionally interchangeable and play key roles in fundamental processes such as dorso-ventral axis formation in metazoans. Because both transcriptional and post-transcriptional mechanisms play central roles in modulating developmental protein levels, we have analyzed the 3'-untranslated region (3'UTR) of the Bmp 2 gene. This 3'UTR is unusually long and is alternatively polyadenylated. Mouse, human, and dog mRNAs are 83-87% identical within this region. A 265-nucleotide sequence, conserved between mammals, birds, frogs, and fish, is present in Bmp2 but not Bmp4. The ability of AmphiBMP2/4, a chordate ortholog to Bmp2 and Bmp4, to align with this sequence suggests that its function may have been lost in Bmp4. Activation of reporter genes by the conserved region acts by a post-transcriptional mechanism. Mouse, human, chick, and zebrafish Bmp2 synthetic RNAs decay rapidly in extracts from cells not expressing Bmp2. In contrast, these RNAs are relatively stable in extracts from Bmp2-expressing cells. Thus, Bmp2 RNA half-lives in vitro correlate with natural Bmp2 mRNA levels. The fact that non-murine RNAs interact appropriately with the mouse decay machinery suggests that the function of these cis-regulatory regions has been conserved for 450 million years since the fish and tetrapod lineages diverged. Overall, our results suggest that the Bmp2 3'UTR contains essential regulatory elements that act post-transcriptionally.