Biochemical characterizations of Pontocerebellar Hypoplasia linked mutations of Target of Egr1 (TOE1) reveal impacts on thermal stability, ribonuclease activity, and oligomerization.

The Target of EGR1 (TOE1) gene encodes the TOE1 deadenylase, which is essential for the maturation of Pol-II transcribed snRNAs in humans. Over a dozen missense mutations in the TOE1 gene have been linked to Pontocerebellar Hypoplasia Type 7 (PCH7), a rare but serious neurodevelopmental and neurodegenerative disease that leads to early mortality. The biochemical mechanisms for why these PCH7-linked mutations alter TOE1's biochemical characteristics remains vague. Here, we utilized AlphaFold predicted structures of TOE1 and biochemical characterizations to investigate the impact of TOE1 variants on TOE1's biochemical properties. We performed characterization of the thermal stability and activity of eleven PCH-linked TOE1 variants and found that eight variants have significant reduced protein thermal stability and only two variants impair TOE1's ribonuclease activity, particularly its exonuclease activity. Additionally, we found that the F148Y mutation impacts TOE1's oligomeric state