Understanding how normal cells become tumorigenic and elucidating the details of the molecular mechanisms underlying this transition is key to our overall understanding of human cancer. Recent work has shown that epigenetic regulation of chromatin plays a central role in transcription, and it is becoming clear that modification of chromatin by BRG1/hBRM-based hSWI/SNF complexes and histone-modifying enzymes such as protein arginine methyltransferase 5 (PRMT5) is involved in the control of cell growth and proliferation. Currently, little is known about the role played by these chromatin-modifying enzymes in human lymphoid malignancies including mantle cell lymphoma (MCL), which remains a fatal disease. Research in MCL has focused on expression analysis of a select number of genes, and to date only very few genes have been identified. We have recently shown that BRG1 and hBRM-associated PRMT5 methylates histone H3 arginine 8 (H3R8) as well as H4R3, and that increased expression of PRMT5 induces transformation by inhibiting transcription of suppressor of tumorigenicity 7 (ST7) and non-metastatic 23-H1 (NM23-H1) tumor suppressor genes. The hypothesis of this project is that PRMTS-mediated symmetric methylation of H3R8 and H4R3 in the promoter region of tumor suppressor genes is involved in the etiology of cancer. The major goal of this application is to define the mechanisms by which hSWI/SNF-associated PRMT5 regulates gene expression and controls cell proliferation. Based on our findings, which show that PRMT5 levels are increased in transformed lymphoid cells including patient-derived MCL cell lines as well as MCL clinical samples, we plan to investigate in specific Aim 1 the molecular mechanisms involved in regulating PRMT5 gene expression.
In specific Aim 2, we propose to study the mechanism by which PRMT5 induces transcriptional repression, and to examine whether there is an inverse relationship between PRMT5 and its target genes in a larger cohort of MCL clinical samples. To enhance our understanding of how hSWI/SNF-associated PRMT5 contributes to the pathogenesis of MCL, experiments in Aim 2 will also focus on using a ChlP-on-Chip platform to delineate the coordinated recruitment of PRMT5 and methylation of H3R8 in normal B cells as well as MCL cells. We have firmly established that S77 and NM23-H1 are direct targets of hSWI/SNF-associated PRMT5. Therefore, experiments in the third Aim will focus on determining whether normalizing ST7 and NM23-H1 expression or knocking down PRMT5 can affect in vivo tumorigenicity of MCL cell lines. These studies will not only allow us to unravel how PRMT5 gene expression becomes aberrant in MCL, but will also allow us to profile PRMTS-mediated epigenetic modification of chromatin that specifies changes in transcriptional performance in MCL cells, and ultimately develop tools to diagnose as well as treat MCL. ? ? ?
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