PLK1

PLK1
Emw · CC BY-SA 3.0 · source
Name	PLK1
Organism	Homo sapiens

PLK1 Polo-like kinase 1 is a serine/threonine protein kinase originally identified in Drosophila melanogaster genetic screens and subsequently characterized in Homo sapiens cell biology. It is a key regulator of the mitotic checkpoint, interacting with components of the Centrosome and Mitotic spindle apparatus to coordinate events from G2 phase entry through Cytokinesis. Research spanning laboratories at institutions such as Harvard University, Max Planck Society, University of Cambridge, and Massachusetts Institute of Technology has connected its activity to pathways involving TP53, RB1, and the Cyclin-dependent kinase network.

Introduction

PLK1 was discovered through comparative genetics linking Drosophila melanogaster polo mutants to mitotic defects observed in mammalian cultured cells from HeLa and COS-7 lines. Subsequent studies at centers including Cold Spring Harbor Laboratory, Stanford University, and the National Institutes of Health mapped its essential role during mitosis, noting conservation across taxa from Saccharomyces cerevisiae to Mus musculus. Clinical interest increased after correlations emerged between PLK1 expression and prognosis in cohorts assembled at Johns Hopkins University and Mayo Clinic.

Structure and Domains

PLK1 is organized with an N-terminal catalytic kinase domain homologous to kinases characterized in Eli Lilly and Company structural studies and a C-terminal polo-box domain (PBD) that mediates substrate recognition. Crystallographic work at institutes such as Diamond Light Source and European Molecular Biology Laboratory resolved the ATP-binding cleft and PBD phosphopeptide-binding pocket, guiding medicinal chemistry programs at Pfizer and Novartis. Domain architecture enables interactions with mitotic proteins like CDC25C, BUB1, and AURORA A, and docking motifs identified by proteomics groups at Broad Institute and European Bioinformatics Institute.

Regulation and Activation

Activation of PLK1 is regulated by phosphorylation and protein–protein interactions involving upstream kinases and phosphatases studied at Max Planck Institute of Biochemistry and University of California, San Francisco. The kinase is activated by phosphorylation on its activation loop by Aurora A in complex with BORA, and negatively regulated by PP2A and feedback from CHK1 and ATM signaling networks characterized by groups at Columbia University and Karolinska Institutet. Cell-cycle dependent transcriptional control involves factors such as E2F1 and repression by TP53, with expression changes observed in datasets from The Cancer Genome Atlas and ENCODE Project.

Cellular Functions

PLK1 orchestrates centrosome maturation, mitotic entry, spindle assembly, chromosome segregation, and cytokinesis processes described in reviews from Nature Reviews Molecular Cell Biology and experimental work at EMBL. Its substrates include CDC25C, PAK1, PRC1, KIF2A, and components of the Anaphase-promoting complex characterized in biochemical assays at Cold Spring Harbor Laboratory and Weizmann Institute of Science. PLK1 localization to kinetochores, spindle poles, and midbody structures is coordinated with complexes involving NDC80, CEP192, and KIF11 as shown by imaging groups at Max Planck Society and University of Oxford.

Role in Cancer and Disease

Aberrant expression and hyperactivation of PLK1 correlate with poor prognosis in multiple malignancies evaluated in cohorts from Memorial Sloan Kettering Cancer Center and MD Anderson Cancer Center, including non-small cell lung carcinoma, colorectal cancer, breast cancer, and acute myeloid leukemia. Functional interactions with tumor suppressors TP53 and oncogenes like MYC drive oncogenic phenotypes described in studies at Dana-Farber Cancer Institute and Fred Hutchinson Cancer Research Center. Beyond oncology, dysregulation has been implicated in developmental defects observed in Zebrafish and Mouse knockout models generated at The Jackson Laboratory and analyzed at European Molecular Biology Laboratory facilities.

Therapeutic Targeting and Inhibitors

PLK1 has been pursued as a drug target by pharmaceutical programs at GlaxoSmithKline, Bayer, and Takeda, producing ATP-competitive inhibitors such as BI 2536 and volasertib, and PBD-targeting molecules developed in academic labs at University of Oxford and ETH Zurich. Clinical trials conducted under protocols at European Medicines Agency and Food and Drug Administration evaluated efficacy in acute myeloid leukemia and solid tumors, with responses reported in multi-center studies involving Royal Marsden Hospital and Vall d'Hebron University Hospital. Combination strategies pairing PLK1 inhibitors with agents targeting PARP or PI3K pathways have been explored at Peter MacCallum Cancer Centre and Institut Gustave Roussy.

Experimental Methods and Assays

Common experimental approaches include in vitro kinase assays using recombinant protein purified in facilities at Addgene and structural studies at Pacific Northwest National Laboratory, RNAi and CRISPR screens performed in core facilities at Broad Institute and Sanger Institute, and high-resolution live-cell microscopy at Max Planck Institute of Molecular Cell Biology and Genetics. Assays for inhibitor potency utilize biochemical IC50 measurements, cell viability assays in lines such as HeLa and MCF7, and xenograft efficacy studies executed at preclinical centers affiliated with Novartis Institutes for BioMedical Research and Eli Lilly and Company.

Category:Protein kinases