Protein arginine methyltransferases (PRMTs) have been implicated in transcriptional activation and repression, but their role in controlling cell growth and proliferation remains obscure. We have recently shown that PRMT5 can interact with flag-tagged BRG1-and hBRM-based hSWI/SNF chromatin remodelers and that both complexes can specifically methylate histones H3 and H4. Here we report that PRMT5 can be found in association with endogenous hSWI/SNF complexes, which can methylate H3 and H4 N-terminal tails, and show that H3 arginine 8 and H4 arginine 3 are preferred sites of methylation by recombinant and hSWI/SNFassociated PRMT5. To elucidate the role played by PRMT5 in gene regulation, we have established a PRMT5 antisense cell line and determined by microarray analysis that more genes are derepressed when PRMT5 levels are reduced. Among the affected genes, we show that suppressor of tumorigenicity 7 (ST7) and nonmetastatic 23 (NM23) are direct targets of PRMT5-containing BRG1 and hBRM complexes. Furthermore, we demonstrate that expression of ST7 and NM23 is reduced in a cell line that overexpresses PRMT5 and that this decrease in expression correlates with H3R8 methylation, H3K9 deacetylation, and increased transformation of NIH 3T3 cells. These findings suggest that the BRG1-and hBRM-associated PRMT5 regulates cell growth and proliferation by controlling expression of genes involved in tumor suppression.During cell growth and proliferation several genes become either repressed or activated. These variations in expression often correlate with changes in chromatin structure, which can be induced by a variety of enzymes that can disrupt nucleosomes in an ATP-dependent manner and/or covalently modify nucleosomal histones (17,29,41,58). Biochemical characterization of different members of the SWI2/SNF2 family of chromatin remodeling complexes revealed that there are complexes that can catalyze both ATP-dependent nucleosome disruption and histone deacetylation (48,49,55,59). Unlike the nucleosome remodeling and deacetylase complex, human SWI/SNF (hSWI/SNF) complexes can be purified either alone or in combination with mSin3A/histone deacetylase, indicating that there are different pools of BRG1-and hBRM-based hSWI/ SNF complexes (19,27,42). Recent work has also shown that flag-tagged BRG1 and hBRM complexes include the type II protein arginine methyltransferase 5 (PRMT5) and that these complexes are involved in transcriptional repression of the MYC/MAX/MAD target gene CAD (32). These studies and work by various groups suggest that ATP-dependent chromatin remodeling complexes can act in concert with various histone-modifying enzymes to modulate chromatin structure (10, 29). Although PRMT5 has been implicated in transcriptional repression of CYCLIN E and CAD, it is not clear whether it is involved in regulating a broader spectrum of genes and whether it has any effects on cell growth and proliferation.Histone methylation has been identified as an important modification for both transcriptional activation and transcript...

Protein arginine methyltransferase PRMT5 interacts with human SWI/SNF complexes and methylates histones H3R8 and H4R3. To elucidate the role of PRMT5 in human cancer, we analyzed PRMT5 expression in normal human B lymphocytes and a panel of lymphoid cancer cell lines as well as mantle cell lymphoma (MCL) clinical samples. We show that PRMT5 protein levels are elevated in all cancer cells, including clinical samples examined despite its low rate of transcription and messenger RNA stability. Remarkably, polysome profiling revealed that PRMT5 mRNA is translated more efficiently in Mino and JeKo MCL cells than in normal B cells, and that decreased miR-92b and miR-96 expression augments PRMT5 translation. Consequently, global methylation of H3R8 and H4R3 is increased and is accompanied by repression of suppressor of tumorigenecity 7 (ST7) in lymphoid cancer cells. Furthermore, knockdown of PRMT5 expression reduces proliferation of transformed JeKo and Raji cells. Thus, our studies indicate that aberrant expression of PRMT5 leads to altered epigenetic modification of chromatin, which in turn impacts transcriptional performance of anti-cancer genes and growth of transformed lymphoid cells.

The role of hSWI/SNF complexes in transcriptional activation is well characterized; however, little is known about their function in transcriptional repression. We have previously shown that subunits of the mSin3A/ histone deacetylase 2 (HDAC2) corepressor complex copurify with hSWI/SNF complexes. Here we show that the type II arginine-specific methyltransferase PRMT5, which is involved in cyclin E repression, can be found in association with Brg1 and hBrm-based hSWI/SNF complexes. We also show that hSWI/SNF-associated PRMT5 can methylate hypoacetylated histones H3 and H4 more efficiently than hyperacetylated histones H3 and H4. Protein-protein interaction studies indicate that PRMT5 and mSin3A interact with the same hSWI/ SNF subunits as those targeted by c-Myc. These observations prompted us to examine the expression profile of the c-Myc target genes, carbamoyl-phosphate synthase-aspartate carbamoyltransferase-dihydroorotase (cad) and nucleolin (nuc). We found that cad repression is altered in cells that express inactive Brg1 and in cells treated with the HDAC inhibitor depsipeptide. Using chromatin immunoprecipitation assays, we found that Brg1, mSin3A, HDAC2, and PRMT5 are directly recruited to the cad promoter. These results suggest that hSWI/SNF complexes, through their ability to interact with activator and repressor proteins, control expression of genes involved in cell growth and proliferation.During cell growth and differentiation several genes become either repressed or activated. These variations in expression often correlate with changes in chromatin structure and occur in the context of the cell cycle. Recruitment of the highly related Brg1 and hBrm chromatin remodeling complexes, which can disrupt nucleosome structure and increase accessibility to DNA, has been implicated in transcriptional activation of many inducible genes (21, 41). However, in view of recent findings, which show that subunits of mSin3/histone deacetylase (HDAC) corepressor complexes can be found in association with Brg1 and hBrm chromatin remodelers and that HDACs 1 and 2 are integral components of the NuRD complex, it appears that ATP-dependent chromatin remodeling might also be involved in transcriptional repression (32,51,56,63,65). Consistent with this notion, mutation of yeast SWI2/ SNF2 can lead to gene derepression (28,35,53). Furthermore, Brg1, hBrm, and

The proper epigenetic modification of chromatin by protein arginine methyltransferases (PRMTs) is crucial for normal cell growth and health. The human SWI/SNF-associated PRMT5 is involved in the transcriptional repression of target genes by directly methylating H3R8 and H4R3. To further understand the impact of PRMT5-mediated histone methylation on cancer, we analyzed its expression in normal and transformed human B lymphocytes. Our findings reveal that PRMT5 protein levels are enhanced in various human lymphoid cancer cells, including transformed chronic lymphocytic leukemia (B-CLL) cell lines. PRMT5 overexpression is caused by the altered expression of the PRMT5-specific microRNAs 19a, 25, 32, 92, 92b, and 96 and results in the increased global symmetric methylation of H3R8 and H4R3. An evaluation of both epigenetic marks at PRMT5 target genes such as RB1 (p105), RBL1 (p107), and RBL2 (p130) showed that promoters H3R8 and H4R3 are hypermethylated, which in turn triggers pocket protein transcriptional repression. Furthermore, reducing PRMT5 expression in WaC3CD5 B-CLL cells abolishes H3R8 and H4R3 hypermethylation, restores RBL2 expression, and inhibits cancer cell proliferation. These results indicate that PRMT5 overexpression epigenetically alters the transcription of key tumor suppressor genes and suggest a causal role of the elevated symmetric methylation of H3R8 and H4R3 at the RBL2 promoter in transformed B-lymphocyte pathology.Enzymes that modify chromatin via arginine methylation have different effects on gene expression, depending on whether they catalyze either the symmetric or asymmetric dimethylation of histones (20,31). Recent work has clearly established a link between the aberrant expression of chromatinmodifying enzymes and cancer; however, the impact protein arginine methyltransferases (PRMTs) have on cell growth and proliferation has only begun to be appreciated. The role PRMTs play in cancer epigenetics remains unexplored, and it is essential to unravel how histone arginine methylation influences cancer. Previous studies have shown that the expression of EZH2, the catalytic subunit of PRC2/3, is altered in cancer cells (19,32,40,41). Similarly, several reports have shown that the interplay and cross-talk between chromatin-modifying enzymes is necessary for the efficient regulation of gene expression, and that changes that affect the activity and/or targeting of chromatin remodelers can trigger cancer (13, 23).Histone methylation has emerged as an important epigenetic modification in the control of chromatin structure and gene expression, and there is little doubt that different epigenetic marks act either synergistically or antagonistically to specify transcriptional performance in various chromatin regions (13). The methylation of histones can be found on both lysine and arginine residues, and both modifications are introduced by SET and PRMT enzymes, respectively. Just like SET proteins, which either can induce or repress transcription, PRMTs either can induce or inhibit transcription depen...

By employing machine learning techniques, we were able to demonstrate that imaging patterns are highly predictive of patient survival. Additionally, we found that GB subtypes have distinctive imaging phenotypes. These results reveal that when imaging markers related to infiltration, cell density, microvascularity, and blood-brain barrier compromise are integrated via advanced pattern analysis methods, they form very accurate predictive biomarkers. These predictive markers used solely preoperative images, hence they can significantly augment diagnosis and treatment of GB patients.