Peptidyl-prolyl cis/trans isomerase (PPIase) that binds to and isomerizes specific phosphorylated Ser/Thr-Pro (pSer/Thr-Pro) motifs. By inducing conformational changes in a subset of phosphorylated proteins, acts as a molecular switch in multiple cellular processes. Displays a preference for acidic residues located N-terminally to the proline bond to be isomerized. Regulates mitosis presumably by interacting with NIMA and attenuating its mitosis-promoting activity. Down-regulates kinase activity of BTK. Can transactivate multiple oncogenes and induce centrosome amplification, chromosome instability and cell transformation. Required for the efficient dephosphorylation and recycling of RAF1 after mitogen activation. Binds and targets PML and BCL6 for degradation in a phosphorylation-dependent manner. Acts as a regulator of JNK cascade by binding to phosphorylated FBXW7, disrupting FBXW7 dimerization and promoting FBXW7 autoubiquitination and degradation: degradation of FBXW7 leads to subsequent stabilization of JUN. May facilitate the ubiquitination and proteasomal degradation of RBBP8/CtIP through CUL3/KLHL15 E3 ubiquitin-protein ligase complex, hence favors DNA double-strand repair through error-prone non-homologous end joining (NHEJ) over error-free, RBBP8-mediated homologous recombination (HR). Upon IL33-induced lung inflammation, catalyzes cis-trans isomerization of phosphorylated IRAK3/IRAK-M, inducing IRAK3 stabilization, nuclear translocation and expression of pro-inflammatory genes in dendritic cells. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Interacts with STIL (By similarity). Interacts with KIF20B. Interacts with NEK6. Interacts (via WW domain) with PRKX. Interacts with BTK. Interacts (via PpiC domain) with DAPK1. Interacts with the phosphorylated form of RAF1. Interacts (via WW domain) with ATCAY; upon NGF stimulation. Interacts with PML (isoform PML-4). Interacts with BCL6. Interacts with FBXW7, disrupting FBXW7 dimerization and promoting FBXW7 autoubiquitination and degradation. Directly interacts with RBBP8/CtIP; this interaction depends upon RBBP8 phosphorylation. Interacts (via WW domain) with IRAK3/IRAK-M in response to IL33-mediated (but not TLR4 ligand LPS) dendritic cell stimulation (By similarity). Colocalizes with NEK6 in the nucleus. Mainly localized in the nucleus but phosphorylation at Ser-71 by DAPK1 results in inhibition of its nuclear localization. The WW domain is required for the interaction with STIL and KIF20B. Phosphorylation at Ser-71 by DAPK1 results in inhibition of its catalytic activity, nuclear localization, and its ability to induce centrosome amplification, chromosome instability and cell transformation (By similarity). Ser-71 is dephosphorylated upon IL33-stimulation of dendritic cells (By similarity).