ABSTRACT
During Drosophila and vertebrate brain development, the conserved transcription factor Prospero/Prox1 is an important regulator of the transition between proliferation and differentiation. Prospero level is low in neural stem cells and their immediate progeny, but is upregulated in larval neurons and it is unknown how this process is controlled. Here, we use single molecule fluorescent in situ hybridisation to show that larval neurons selectively transcribe a long prospero mRNA isoform containing a 15 kb 3’ untranslated region, which is bound in the brain by the conserved RNA-binding protein Syncrip/hnRNPQ. Syncrip binding increases the mRNA stability of the long prospero isoform, which allows an upregulation of Prospero protein production. Our findings highlight a regulatory strategy involving alternative polyadenylation followed by differential post-transcriptional regulation.
Footnotes
In this manuscript, we report that Prospero protein levels are regulated through mRNA stability, depending on the RNA binding protein, Syncrip, and the inclusion of an extremely long pros 3 UTR. In the original version of the manuscript we used a nonsense-mediated mRNA decay mutant to remove the long isoform of pros, and reported that the neuroblasts in the line did not terminate correctly. However, we later discovered that the proslong isoform was unaffected in the mutant and a stock contamination was responsible for our results. Therefore, the results previously described in Figures 3 E,G,I and 6 are invalid. We have now produced an alternative transgenic line, using a transcriptional terminator to remove the long isoform of pros. The new proslong mutant terminates pupal neuroblast division normally. As a consequence, we have refocused the paper on the regulation of Prospero level in larval neurons. This substantial change to the paper involves a new title, many updated figures (with improved four-colour imaging of protein and mRNA) and the removal of data that are no longer relevant to the story.
