This is a Shannon Award providing partial support for the research projects that fall short of the assigned institute's funding range but are in the margin of excellence. The Shannon Award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. Kinase inhibitory proteins, KIPs, negatively regulate the activity of the G1-cyclin/cyclin-dependent kinase (CDK) complexes in response to signals that arrest cell proliferation. We have recently discovered that p27KIP1 negatively regulates cyclin E associated kinase activity in response to TGFbeta-treatment or density dependent inhibition of growth. In addition, p27KIP1 activity can also associate with cyclin D-associated kinases. Because p27KIP1 is present, but inactive, in proliferating cells it may have a role in regulating G1 progression. Two models have been proposed to explain this role in G1 progression. Model 1 places P27KIP1 in a role where it sets the threshold level of G1- cyclin accumulation necessary to allow a cell to enter into S-phase. Model 2 supposes that p27KIP1 may constrain the activation of cyclin E- associated kinase in the absence of the cyclin D-associated kinase. The current data available supports both models equivalently. The goal of this proposal is to determine the role of p27KIP1 in the cell cycle with reference to these two models. In particular, we will i) examine the effects of modulating p27KIP1 expression, both positively and negatively, on G1 progression, ii) we will determine the regulation of p27KIP1 both transcriptionally and translationally, and iii) ultimately determine the proteins that interact with P27KIP1 to modulate its functions during cellular proliferation. The expression of the cyclin E associated kinase is rate-limiting for G1 progression and also essential for progression of embryonic cells into S-phase. In addition, cyclin E mutations occur frequently in breast cancer cell lines, suggesting that inappropriate activation of cyclin E- associated kinases may be part of the tumorigenic process. p27KIP1 regulates the expression of the cyclin E-associated kinase by physically interacting with this kinase and preventing its activation. Consequently, it may be that mutation of cyclin E, in breast cancer cell lines, allows it to escape from growth regulation by p27KIP1. To address this we first need to understand both the role of p27KIP1 in cell proliferation, and how p27KIP1 is regulated during cell proliferation. These are the goals of this project, and the significance may be in gaining a better understanding of the tumorigenic process in tumors that have inappropriately activated cyclin E.
