Upstream open reading frames control PLK4 translation and centriole duplication in primordial germ cells

Abstract

In this study, Phan et al. show that PLK4 abundance is translationally controlled through conserved upstream open reading frames (uORFs) in the 5′ UTR of the mRNA and that Plk4 uORFs suppress Plk4 translation and prevent excess protein synthesis. Their data uncover a specific requirement for uORF-dependent control of PLK4 translation in counterbalancing the increased Plk4 transcription in PGCs.

Abstract

Centrosomes are microtubule-organizing centers comprised of a pair of centrioles and the surrounding pericentriolar material. Abnormalities in centriole number are associated with cell division errors and can contribute to diseases such as cancer. Centriole duplication is limited to once per cell cycle and is controlled by the dosage-sensitive Polo-like kinase 4 (PLK4). Here, we show that PLK4 abundance is translationally controlled through conserved upstream open reading frames (uORFs) in the 5′ UTR of the mRNA. Plk4 uORFs suppress Plk4 translation and prevent excess protein synthesis. Mice with homozygous knockout of Plk4 uORFs ( Plk4 ^{Δ u/Δ u} ) are viable but display dramatically reduced fertility because of a significant depletion of primordial germ cells (PGCs). The remaining PGCs in Plk4 ^{Δ u/Δ u} mice contain extra centrioles and display evidence of increased mitotic errors. PGCs undergo hypertranscription and have substantially more Plk4 mRNA than somatic cells. Reducing Plk4 mRNA levels in mice lacking Plk4 uORFs restored PGC numbers and fully rescued fertility. Together, our data uncover a specific requirement for uORF-dependent control of PLK4 translation in counterbalancing the increased Plk4 transcription in PGCs. Thus, uORF-mediated translational suppression of PLK4 has a critical role in preventing centriole amplification and preserving the genomic integrity of future gametes.