The UBR box E3 ligases Poe and Hyd are required for efficient Pericentrin degradation

Abstract

Centrosomes are the major microtubule organizing centers (MTOC) of many cells and are composed of centrioles and the pericentriolar material (PCM). Centrosomes are an essential part of diverse cellular processes and require precise regulation of their protein levels. One protein whose levels must be regulated is Pericentrin (PCNT in humans and PLP in Drosophila). Increased PCNT expression and its protein accumulation is linked to clinical conditions including cancer, mental disorders, and ciliopathies. However, the mechanisms by which PCNT levels are regulated remains underexplored. Our previous study (Galletta, 2020) demonstrated that PLP levels are sharply downregulated during early spermatogenesis and this regulation is essential to spatially position PLP on the proximal end of centrioles. We hypothesized that the sharp drop in PLP protein was a result of a rapid protein degradation during the male pre-meiotic G2 phase. In this study we show that the N-terminal region of PLP is required for regulating its levels, which when elevated, extends PLP position distally on centrioles. Consequently, PCM was also mispositioned leading to defects in spermatids. We then performed a targeted screen where we identified the E2 ligases, Rad6 and UbcD1, and the UBR box family E3 ligases, Poe (UBR4) and Hyd (UBR5) as factors that promote PLP degradation in spermatocytes. Collectively, our study suggests that Poe and Hyd directly bind the N-terminus of PLP and target it for degradation, ensuring proper centriole/basal body assembly and male fertility.