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Research Abstracts Online
January 2009 - March 2010

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University of Minnesota Twin Cities
Medical School
Department of Pediatrics

PI: Timothy C. Hallstrom

Genome-wide shRNA Screen to Identify Regulators of RB/E2F Apoptosis Induction

Most cancers arise when cells sustain oncogenic mutations that drive proliferation and secondary mutations that block oncogene induced apoptosis. The retinoblastoma gene (RB) is one of the most commonly mutated tumor suppressors in cancer. The retinoblastoma protein (pRb) regulates cell cycle progression and tumorigenesis through its repression of a family of transcription factors called E2Fs. The E2F family of transcription factors, which become deregulated in human cancers that have lost pRb function, normally promote expression of genes involved in cell cycle division and proliferation. E2Fs also paradoxically promote expression of apoptosis inducing genes like p53 as a mechanism to eliminate incipient cancer cells. Many of the E2F1 regulated apoptosis inducing genes are tumor suppressors mutated in various cancers. The goals of this project are: to identify which genes control Rb/E2F1 induced apoptosis; to test whether defects in these regulons lead to tumorigenesis; and to determine if this knowledge can be used to enhance current chemotherapy.

To this end, these researchers are utilizing genome-wide short-hairpin RNA (shRNA) library technology to screen for regulators of E2F1-induced apoptosis. shRNA is a technique, based on RNA interference (RNAi), used to target a specific gene’s messenger RNA for degradation, thus effectively lowering the levels of expression of that gene in a cell. The fundamental premise of the screen is that degrading messenger RNA (mRNA) of genes essential for E2F1 apoptosis induction will cause these cells to resist E2F1 adenoviral infection, allowing identification of the resistance promoting shRNA sequences. Identification of E2F-induced apoptotic pathways is expected to identify novel tumor suppressor genes that may also be suitable targets for chemotherapeutic intervention aiming to restore E2F1 mediated apoptosis to kill cancer cells.

Group Members

Xudong Liang, Research Associate
Huarui Lu, Research Associate