Acta Biochim Biophys Sin (Shanghai) 2019 Apr 16. Epub 2019 Apr 16.
Protein Science Laboratory of the Ministry of Education, School of Life Science, Tsinghua University, Beijing, China.
Molluscan shell is a biomineral that consists of a highly organized calcium carbonate composite. Organisms mainly use matrix proteins to elaborately control the biomineralization process, but knowledge of their regulatory mechanisms is limited. The transcription factor Pf-Rel, which belongs to the Rel/nuclear factor-κB family, was shown to regulate transcription at the Nacrein promoter in the pearl oyster Pinctada fucata. Here, we further explored the transcriptional regulation mechanisms of Pf-Rel on the matrix proteins Prismalin-14 and MSI60. The relative expression levels of Prismalin-14 and MSI60 were high in the mantle edge and mantle pallial tissues of P. fucata. These three genes were significantly up-regulated after shell notching, suggesting that they might play important roles during shell formation. Importantly, Pf-Rel gene knockdown by RNA interference led to down-regulation of Prismalin-14 and MSI60 expression. In transient co-transfection assays, Pf-Rel significantly up-regulated the promoter activities of the Prismalin-14 and MSI60 genes in a dose-dependent manner. Furthermore, the promoter regions of Prismalin-14 (-1794 to -1599 bp) and MSI60 (-2244 to -1141 bp) were required for the activation by Pf-Rel. Altogether, these results suggest that the transcription factor Pf-Rel can up-regulate the expression of the matrix protein genes Prismalin-14 and MSI60 during shell formation in P. fucata, which improves our understanding of transcription regulation at the molecular level during molluscan shell development.