The yeast Ess1 prolyl isomerase controls Swi6 and Whi5 nuclear localization.
The Ess1 prolyl isomerase from Saccharomyces cerevisiae and its human ortholog, Pin1, play critical roles in transcription by regulating RNA polymerase II. In human cells, Pin1 also regulates a variety of signaling proteins, and Pin1 misexpression is linked to several human diseases. To gain insight into Ess1/Pin1 function, we carried out a synthetic genetic array screen to identify novel targets of Ess1 in yeast. We identified potential targets of Ess1 in transcription, stress, and cell-cycle pathways. We focused on the cell-cycle regulators Swi6 and Whi5, both of which show highly regulated nucleocytoplasmic shuttling during the cell cycle. Surprisingly, Ess1 did not control their transcription but instead was necessary for their nuclear localization. Ess1 associated with Swi6 and Whi5 in vivo and bound directly to peptides corresponding to their nuclear localization sequences in vitro. Binding by Ess1 was significant only if the Swi6 and Whi5 peptides were phosphorylated at Ser-Pro motifs, the target sites of cyclin-dependent kinases. On the basis of these results, we propose a model in which Ess1 induces a conformational switch (cis-trans isomerization) at phospho-Ser-Pro sites within the nuclear targeting sequences of Swi6 and Whi5. This switch would promote nuclear entry and/or retention during late M and G1 phases and might work by stimulating dephosphorylation at these sites by the Cdc14 phosphatase. This is the first study to identify targets of Ess1 in yeast other than RNA polymerase II.
Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210.
David
D
Atencio
Cassandra
C
Barnes
Thomas M
TM
Duncan
Ian M
IM
Willis
Steven D
SD
Hanes
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism*; D016193:G1 Phase; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C074860:CDC14 protein, S cerevisiae; D018797:Cell Cycle Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D012097:Repressor Proteins; C075111:SWI6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C508130:Whi5 protein, S cerevisiae; D017027:Protein Tyrosine Phosphatases; C000606845:ESS1 protein, S cerevisiae; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase
biolayer interferometry; cyclin-dependent kinase sites; nuclear import; proline isomerase