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...

AcKNoWLedgeMeNTSWe acknowledge the financial support from the NIH grant CA 102264. AbSTRAcTCurcumin, a major active component of turmeric, is known to induce apoptosis in several types of cancer cells, but little is known about its activity in chemoresistant cells. Hence, the aim of the present study was to investigate the anticancer properties of curcumin in cisplatin-resistant human ovarian cancer cells in vitro. The results indicated that curcumin inhibited the proliferation of both cisplatin-resistant (CR) and sensitive (CS) human ovarian cancer cells almost equally. Enhanced superoxide generation was observed in both CR and CS cells treated with curcumin. Curcumin induced G 2 /M phase cell-cycle arrest in CR cells by enhancing the p53 phosphorylation and apoptosis through the activation of caspase-3 followed by PARP degradation. Curcumin also inhibited the phosphorylation of Akt while the phosphorylation of p38 MAPK was enhanced. In summary, our results showed that curcumin inhibits the proliferation of cisplatin-resistant ovarian cancer cells through the induction of superoxide generation, G 2 /M arrest, and apoptosis.

No abstract

Graphical abstract

Tumor suppressor protein, TP53 also known as the "guardian of the genome" plays a key role in preventing malignant transformation. Almost 50% of human tumors carry mutations in this gene; in the remaining tumors, the TP53 network is functionally inoperative. The majority of TP53 mutations are missense mutations and more than 90% of the missense mutations affect specific codons in the DNA-binding domain, called "hotspot codons." The present study was aimed at analyzing the germline mutation status of four hotspot codons in TP53 namely, codon 175, codon 245, codon 248 (within the DNA binding domain) and codon 72 (outside the DNA binding domain) in cancer cases encountered in a tertiary care hospital in South India by PCR-RFLP. The case-control study included 85-10 subjects respectively. The results of the study indicated that majority of the cancer cases did not harbor germline mutations in the four hot spot codons of TP53. The study further highlights the usefulness of PCR-RFLP as a simple and cost effective tool for checking gene mutations.