Orb-dependent polyadenylation contributes to PLP expression and centrosome scaffold assembly

Abstract

As the microtubule-organizing centers (MTOCs) of most cells, centrosomes engineer the bipolar mitotic spindle required for error-free mitosis. Drosophila Pericentrin (PCNT)-like protein (PLP) is a key centrosome component that directs formation of a pericentriolar material (PCM) scaffold required for PCM organization and MTOC function. Here, we investigate the post-transcriptional regulation of plp mRNA. We identify conserved binding sites for cytoplasmic polyadenylation element binding (CPEB) proteins within the plp 3’-untranslated region and examine the role of the CPEB ortholog, oo18 RNA-binding protein (Orb), in plp mRNA regulation. Our data show Orb biochemically interacts with plp mRNA and promotes PLP protein expression. Loss of orb, but not orb2, diminishes PLP levels in embryonic extracts. Consequently, PLP localization to centrosomes and function in PCM scaffolding is compromised in orb mutant embryos, resulting in genome instability and embryonic lethality. Moreover, we find PLP over-expression can restore centrosome scaffolding and rescue the cell division defects caused by orb depletion. Our data suggest Orb modulates PLP expression at the level of plp mRNA polyadenylation and showcases the post-transcriptional regulation of core, conserved centrosomal mRNAs as critical for centrosome function.