Novel roles for p27 as transcriptional co-regulator of cJun in stem cells and development

Information

  • Research Project
  • 10246403
  • ApplicationId
    10246403
  • Core Project Number
    R01CA253111
  • Full Project Number
    5R01CA253111-02
  • Serial Number
    253111
  • FOA Number
    PA-19-056
  • Sub Project Id
  • Project Start Date
    9/1/2020 - 3 years ago
  • Project End Date
    8/31/2025 - a year from now
  • Program Officer Name
    MIETZ, JUDY
  • Budget Start Date
    9/1/2021 - 2 years ago
  • Budget End Date
    8/31/2022 - a year ago
  • Fiscal Year
    2021
  • Support Year
    02
  • Suffix
  • Award Notice Date
    8/13/2021 - 2 years ago
Organizations

Novel roles for p27 as transcriptional co-regulator of cJun in stem cells and development

Project Summary p27 is a CDK inhibitor that limits normal cell proliferation. We showed p27 C-terminal phosphorylation at T157 and T198 by AKT increases in mid G1 and p27pT157pT198 (p27pTpT) facilitates interaction with novel protein partners. We recently showed C-terminal p27pTpT phosphorylation promotes its association with cJun. Genomic profiling showed p27 is co-recruited with cJun to over half of cJun chromatin binding sites to either activate or repress target genes. p27/cJun activated targets include TGFB2, and are associated with EMT, and programs that upregulate stem cells and alter cell adhesion and migration. Profiles of target genes repressed by p27/cJun suggest that p27pTpT opposes tissue differentiation. A subset of p27/cJun target genes bind to a STAT3 consensus motif and p27, cJun and STAT3 all appear to bind and co-regulate cMYC. Notably, p27pTpT is a driver of stem cell potency: cellular p27pTpT upregulates spheres, SOX2, NANOG and cMYC and tumor initiating cells in vivo. Our TG-p27CK-DD mice transgenic for a p27 phosphomimetic mutant that fails to bind cyclin/CDKs, show multi-organ overgrowth and increased size, suggesting that p27CK-DD abrogates WTp27 actions to restrain normal stem and progenitor expansion. This grant investigates the role of p27 as a transcriptional regulator in normal cells and development. Our data support the hypothesis that WTp27 plays important transcriptional roles during differentiation, to limit stem and progenitor cell expansion in various tissues. In contrast, upon C-terminal phosphorylation, p27 interacts with cJun, STAT3 and other factors to expand or maintain tissue stem or progenitor cells and oppose differentiation. We will compare p27WT, p27CDK and p27CK-DD MEFS in AIM1 to evaluate how p27 interacts with cJun and STAT3 on chromatin to govern gene expression across the cell cycle from G0, to mid-G1 and the G1/S phase transition. We will investigate if increased C-terminal p27 phosphorylation alters co-regulator and target gene selection and abrogates the co-repressive functions of p27 in quiescent cells. In AIM2, we will separate actively transcribed euchromatin from transcriptionally inactive heterochromatin and carry out ChIP-seq and ChIP-Mass Spec to identify the chromatin associated p27 interactome involved in transactivator versus repressor complexes. AIM3 will study mouse development, tissue differentiation, and adult stem and progenitor populations in TG-p27CK- DD and TG-p27CK- mice. We will test if p27CK-DD confers stronger reprogramming potential on MEFs and disrupts differentiation of iPSC into embryoid bodies. This work will elucidate a novel function of p27 as a phosphorylation-dependent transcriptional regulator with implications for tissue stem cell control and potential applications in regenerative medicine. Controlled modulation of p27, or of p27 target genes identified herein, might offer potential to expand or regenerate hematologic and other tissues. Understanding how p27/cJun transcriptional programs regulate tissue development might identify new therapeutic targets to be exploited for tissue regeneration and illuminate other human diseases at the interface of differentiation and growth control.

IC Name
NATIONAL CANCER INSTITUTE
  • Activity
    R01
  • Administering IC
    CA
  • Application Type
    5
  • Direct Cost Amount
    388826
  • Indirect Cost Amount
    200005
  • Total Cost
    588831
  • Sub Project Total Cost
  • ARRA Funded
    False
  • CFDA Code
    393
  • Ed Inst. Type
    SCHOOLS OF MEDICINE
  • Funding ICs
    NCI:588831\
  • Funding Mechanism
    Non-SBIR/STTR RPGs
  • Study Section
    CSRS
  • Study Section Name
    Cellular Signaling and Regulatory Systems Study Section
  • Organization Name
    GEORGETOWN UNIVERSITY
  • Organization Department
    INTERNAL MEDICINE/MEDICINE
  • Organization DUNS
    049515844
  • Organization City
    WASHINGTON
  • Organization State
    DC
  • Organization Country
    UNITED STATES
  • Organization Zip Code
    200570001
  • Organization District
    UNITED STATES