PLAUF binding to the 3′UTR of the H3.3 histone transcript affects mRNA stability

In P. lividus sea urchin the H3.3 histone variant is coded by an mRNA characterized by a long 3′UTR containing ARE (AU-Rich element) motifs. RNA stability assays performed in rabbit reticulocyte lysate showed that such 3′UTR affects the degradation rate of the transcripts. In fact, chimeric molecules containing the 3′UTR of H3.3 transcript, ligated to the coding region of the rabbit β-globin transcript, were unstable whereas chimeric molecules containing mainly the coding region of the H3.3 transcript were stable as the wild-type globin mRNA.Three proteins (45kDa, 32kDa and 25kDa) that bind specifically the 3′UTR have been revealed in the whole protein extracts of embryos at different stages of development. PLAUF, a P. lividus RNA-binding protein similar to human and rodent AUF1 proteins, was identified as the 32kDa factor using anti-PLAUF antibody in Western blot and supershift mobility assays. Moreover the recombinant GST–PLAUF protein specifically binds part of the H3.3 3′UTR and in vitro affects the half-life of the transcript. In addition in situ hybridization experiments demonstrated that PLAUF and H3.3 histone mRNAs co-localize in embryos at different stages of development. In conclusion all the reported results suggest that PLAUF can bind in vivo the 3′UTR of the H3.3 histone mRNA and plays some role in the stability of the mRNA.