title: Prolyl isomerase Pin1 regulates transcription factor LSF (TFCP2) by facilitating dephosphorylation at two serine-proline motifs.
abstract: Transcription factor LSF is essential for cell cycle progression, being required for activating expression of the thymidylate synthase (Tyms) gene at the G1/S transition. We previously established that phosphorylation of LSF in early G1 at Ser-291 and Ser-309 inhibits its transcriptional activity and that dephosphorylation later in G1 is required for its reactivation. Here we reveal the role of prolyl cis-trans isomerase Pin1 in activating LSF, by facilitating dephosphorylation at both Ser-291 and Ser-309. We demonstrate that Pin1 binds LSF both in vitro and in vivo. Using coimmunoprecipitation assays, we identify three SP/TP motifs in LSF (at residues Ser-291, Ser-309, and Thr-329) that are required and sufficient for association with Pin1. Co-expression of Pin1 enhances LSF transactivation potential in reporter assays. The Pin1-dependent enhancement of LSF activity requires residue Thr-329 in LSF, requires both the WW and PPiase domains of Pin1, and correlates with hypophosphorylation of LSF at Ser-291 and Ser-309. These findings support a model in which the binding of Pin1 at the Thr-329-Pro-330 motif in LSF permits isomerization by Pin1 of the peptide bonds at the nearby phosphorylated SP motifs (Ser-291 and Ser-309) to the trans configuration, thereby facilitating their dephosphorylation.
authors.affiliation: Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
authors.forename: Utsav H
authors.initials: UH
authors.lastname: Saxena
authors.forename: Laura
authors.initials: L
authors.lastname: Owens
authors.forename: Julie R
authors.initials: JR
authors.lastname: Graham
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Cooper
authors.forename: Ulla
authors.initials: U
authors.lastname: Hansen
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; C501905:Tfcp2 protein, mouse; D014157:Transcription Factors; D019696:Peptidylprolyl Isomerase; C000606850:Pin1 protein, mouse