Two human proteins, p21 and p27, bind to and regulate cyclin-dependent kinases (Cdks), the master time- keepers of eukaryotic cell division. p21 and p27 are intrinsically unstructured proteins. Importantly, the intrinsic flexibility of p27 mediates sequential folding upon binding to Cdk/cyclin complexes. While lacking tertiary structure, p27 exhibits partially folded local structural elements prior to binding Cdk/cyclin complexes, which influences the sequential binding mechanism. The PI's group recently elucidated a two-step phosphorylation mechanism that relieves p27-mediated inhibition of Cdk2 through tyrosine (step 1) and threonine (step 2) phosphorylation of p27. After phosphorylation on tyrosine 88, Cdk2 itself phosphorylates p27 on threonine 187, targeting it for ubiquitination and degradation. Tyrosine kinases that promote cell proliferation were shown to initiate this two-step mechanism that eliminates p27-mediated cell cycle arrest at the G1/S checkpoint. In addition, it was shown that Bcr-Abl, the constitutively active, causative oncogene associated with some types of leukemia, drives cell proliferation by over-activating the two-step p27 phosphorylation of p27. NMR studies of phosphorylated p27 bound to Cdk2/cyclin A revealed the critical role that p27 flexibility plays in this two step phosphorylation mechanism, highlighting the role of intrinsic disorder in diverse regulatory function. We propose to marshal our significant expertise with p27 and Cdk2/cyclin A to extend our studies to other Cdk/cyclin complexes to comprehensively understand how p21 and p27 regulate cell division. These studies will not only provide insights into the fundamental mechanisms that control division in normal cells, but also will provide knowledge relevant to how these control mechanisms are corrupted in cancer cells. The four specific aims are: 1) To determine the effect of phosphorylation (of p27) on tyrosine 74 (Y74) by Src on the activity of p27 toward Cdk2/cyclin A. We will determine how Y74 phosphorylation, alone and in combination with tyrosine 88 (Y88) phosphorylation by Abl, alters the activity of p27 toward Cdk2/cyclin A using biochemical, biophysical and structural methods; 2) To determine the relevance of the two-step p27 phosphorylation/regulatory mechanism discovered for Cdk2/cyclin A to the regulation of other Cdk/cyclin complexes, including Cdk4/cyclin D1 and Cdk1/cyclin E2; 3) To determine the relevance of our discoveries concerning p27 phosphorylation to the related cell cycle regulator, p21; and 4) To investigate relationships between intrinsic flexibility and function for the different sub-domains of p27 and p21. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA082491-07
Application #
7502096
Study Section
Macromolecular Structure and Function B Study Section (MSFB)
Program Officer
Knowlton, John R
Project Start
2001-07-01
Project End
2012-07-31
Budget Start
2008-09-01
Budget End
2009-07-31
Support Year
7
Fiscal Year
2008
Total Cost
$214,402
Indirect Cost
Name
St. Jude Children's Research Hospital
Department
Type
DUNS #
067717892
City
Memphis
State
TN
Country
United States
Zip Code
38105
Phillips, Aaron H; Ou, Li; Gay, Alexandre et al. (2018) Mapping Interactions between p27 and RhoA that Stimulate Cell Migration. J Mol Biol 430:751-758
Follis, Ariele Viacava; Llambi, Fabien; Kalkavan, Halime et al. (2018) Regulation of apoptosis by an intrinsically disordered region of Bcl-xL. Nat Chem Biol 14:458-465
Ragavan, Mukundan; Iconaru, Luigi I; Park, Cheon-Gil et al. (2017) Real-Time Analysis of Folding upon Binding of a Disordered Protein by Using Dissolution DNP?NMR Spectroscopy. Angew Chem Int Ed Engl 56:7070-7073
Ban, David; Iconaru, Luigi I; Ramanathan, Arvind et al. (2017) A Small Molecule Causes a Population Shift in the Conformational Landscape of an Intrinsically Disordered Protein. J Am Chem Soc 139:13692-13700
Banerjee, Priya R; Mitrea, Diana M; Kriwacki, Richard W et al. (2016) Asymmetric Modulation of Protein Order-Disorder Transitions by Phosphorylation and Partner Binding. Angew Chem Int Ed Engl 55:1675-9
Das, Rahul K; Huang, Yongqi; Phillips, Aaron H et al. (2016) Cryptic sequence features within the disordered protein p27Kip1 regulate cell cycle signaling. Proc Natl Acad Sci U S A 113:5616-21
Grace, Christy R; Ban, David; Min, Jaeki et al. (2016) Monitoring Ligand-Induced Protein Ordering in Drug Discovery. J Mol Biol 428:1290-1303
Csizmok, Veronika; Follis, Ariele Viacava; Kriwacki, Richard W et al. (2016) Dynamic Protein Interaction Networks and New Structural Paradigms in Signaling. Chem Rev 116:6424-62
Huang, Yongqi; Yoon, Mi-Kyung; Otieno, Steve et al. (2015) The activity and stability of the intrinsically disordered Cip/Kip protein family are regulated by non-receptor tyrosine kinases. J Mol Biol 427:371-386
Follis, Ariele Viacava; Llambi, Fabien; Merritt, Parker et al. (2015) Pin1-Induced Proline Isomerization in Cytosolic p53 Mediates BAX Activation and Apoptosis. Mol Cell 59:677-84

Showing the most recent 10 out of 47 publications