Ms Hay Hui Sin
Hui Sin has been awarded 2nd Prize in the 2012 Johnson & Johnson Asia Outstanding Graduate Thesis Award in Bio-tech. This is a highly competitive international award and she is one of the two students who won from NUS. Hui Sin is currently a PhD student in Dr Alan Prem Kumar’s laboratory. Her thesis project is supported by funds from CSI Experimental Therapeutics Program, NMRC grant to Dr Alan Prem Kumar, and core funding from Institute of Molecular and Cell Biology, A*STAR to her co-supervisor, Associate Professor Vinay Tergaonkar.
Ms Phyllis Chong
Phyllis has been awarded 1st runner-up for the Best Oral Presentation for the YLLSOM 2nd Annual Graduate Scientific Congress held on 15 Feb 2012. More than 130 abstracts were submitted for this symposium and Phyllis’s abstract was shortlisted for oral presentation. She is currently in A/Prof Chng Wee Joo’s group at CSI Singapore
Title: Global discovery of dysregulated protein expression and phosphorylation networks identifies Leo1 as a key substrate of PRL-3 phosphatase in leukemogenesis
Abstract: Dysregulation of PRL-3 phosphatase is associated with human malignancy, with overexpression correlating with invasiness, metastasis and poor prognosis. Recently, our group demonstrated that PRL-3 is a novel oncogene in acute myeloid leukemia (AML), when stable expression confers cytokine independency, increased self-renewal, and tumorigenesis in NOD/SCID mice. Despite compelling evidence establishing PRL-3 as a promising therapeutic target, this intervention is premature until the mechanisms of PRL-3 mediated signaling are understood.
To elucidate the physiological and pathological substrates of PRL-3, we probed the phosphoproteome in AML cells stably overexpressing PRL-3 by combining global phosphopeptide enrichment and tandem mass spectrometry (MS). Analysis of the 846 phosphopeptides differentially regulated by PRL-3 revealed novel functions of PRL-3 such as pre-mRNA processing and protein metabolism. Our dataset suggests that PRL-3 dephosphorylates and induces the expression of Leo1, a component of the human RNA polymerase II-associated factor (hPAF) complex, which consists also PD2, hCtr9, hSki8 and parafibromin. Of special note, PD2 and Ctr9 were also differentially regulated in our PRL-3 cells, representing three out of five subunits of the hPAF complex. Interestingly, these subunits have opposing functions in cancer, leading to a need to characterize them in a context-dependent manner.
Here, we show that PRL-3 induce Leo1 expression at both the mRNA and protein level, conversely, Leo1 expression decreases upon knockdown of PRL-3. We also found Leo1 to be highly expressed in AML cell lines but at lower levels in normal peripheral blood cells. Leo1 expression is found mainly in the nuclear compartment, where PRL-3 is also present; further work will confirm the direct interaction and dephosphorylation of Leo1 by PRL-3. Also, to understand how Leo1 may be a mediator of PRL-3′s oncogenic activity, we investigated histone modifications as a known function of hPaf complex. We observed a marked reduction of repressive histone marks (H3K9me2,3 and H3K27me2,3). Further studies will explore the oncogenic potential of Leo1 through regulation of histone methylation leading to abberant gene expression.