Nuclear Poly(A) Binding Protein 1 (PABPN1) Mediates Zygotic Genome Activation-dependent Maternal mRNA Clearance During Mouse Early Embryonic Development

An embryo starts its life with maternal mRNA clearance, which is crucial for embryonic development. The elimination of maternal transcripts occurs by the joint action of two pathways: the first is a maternally encoded mRNA decay pathway (M-decay), while the second is zygotic genome activation (ZGA)-dependent pathway (Z-decay). However, the zygotic factors triggering maternal mRNA decay in early mammalian embryos remain largely unknown. In this study, we identify the zygotically encoded nuclear poly(A) binding protein 1 (PABPN1) as a factor required for maternal mRNA turnover, with an unpredictable cytoplasmic function. Cytoplasmic PABPN1 docks on 3ʹ-uridylated transcripts, downstream of terminal uridylyl transferases TUT4 and TUT7, and recruits 3ʹ-5ʹ exoribonuclease DIS3L2 to its targets, facilitating the decay of maternal mRNA. Pabpn1-knockout in mice resulted in preimplantation-stage mortality, due to early developmental arrest at the morula stage. This study characterizes the presence of a zygotic destabilizer of maternal mRNA and helps in elucidating the Z-decay process mechanisms, which potentially contribute to human fertility. Zygotes, 2-cell, and 8-cell embryos of WT and Pabpn1 knockdown for replicates are performed RNA sequencing. 2-cell embryos of control and Dis3l2 knockdown for replicates are performed RNA sequencing.