Modification of the transcription factor FOXL2 at serines 101 and 107 disables DNA binding, leads to nucleolar relocalization, and rewires granulosa-cell programs

We demonstrate that FOXL2 is phosphorylated by PKC in vitro on several residues and that these modifications alter FOXL2 localization and activity. Specifically, phosphorylation of the FHD residues Ser101 and Ser107 by PKC are expected to lead to major changes in FOXL2 properties. Consistently, the phosphomimetic substitutions S101D and S107D abolish DNA binding and drives nucleolar enrichment. RNA-seq shows that S101D and a C-terminal truncation (ΔC) produce broad loss-of-function (LOF) indicating that DNA engagement and the C-terminus are required for full transcriptional output. We also observed variant-specific gain-of-function (GOF) effects. By contrast, S101A perturbs few transcripts.