Identification and characterization of novel spliced variants of PRMT2 in breast carcinoma

Abstract

Protein N-arginine methyltransferases (PRMTs) participate in a number of cellular processes, including cell growth, nuclear ⁄ cytoplasmic protein shuttling, differentiation, RNA splicing and post-transcriptional regulation. PRMT2 (also known as HRMT1L1) is clearly involved in lung function, the inflammatory response, apoptosis promotion, Wnt signaling and leptin signaling regulation through different mechanisms. In this study, we report the molecular and cell biological characterization of three novel PRMT2 splice variants isolated from breast cancer cells and referred to as PRMT2a, PRMT2b and PRMT2c. Compared with the wild-type PRMT2, these variants lack different motifs and therefore generate distinct C-terminal domains. Confocal microscopy scanning revealed a distinct intracellular localization of PRMT2 variants, suggesting that the alternatively spliced C-terminus of PRMT2 can directly influence its subcellular localization. Our findings reveal that these variants are capable of binding to estrogen receptor alpha (ERa) both in vitro and in vivo, and the N-terminal regions of these variants contribute to ERa-PRMT2 interactions. Furthermore, these variants were proved to be able to enhance ERa-mediated transactivation activity. Luciferase reporter assays showed that PRMT2s could modulate promoter activities of the ERa-targeted genes of Snail and E-cadherin. In addition, PRMT2 silencing could enhance 17b-estradiol-induced proliferation by regulating E2F1 expression and E2F1-responsive genes in ERa-positive breast cancer cells. Real-time PCR and immunohistochemistry showed that overall PRMT2 expression was upregulated in breast cancer tissues and significantly associated with ERa positivity status both in breast cancer cell lines and breast cancer tissues. We speculate that PRMT2 and its splice variants may directly modulate ERa signaling and play a role in the progression of breast cancer. Structured digital abstractl PRMT2 and AR colocalize by fluorescence microscopy (View interaction) l PRMT2 physically interacts with AR by anti tag coimmunoprecipitation (View interaction) l PRMT2 physically interacts with ER-alpha by anti tag coimmunoprecipitation (View interaction) l PRMT2 binds to ER-alpha by pull down (View interaction) l PRMT2 physically interacts with ER-alpha by pull down (View interaction) l ER-alpha and PRMT2 colocalize by fluorescence microscopy (View interaction) Abbreviations AR, androgen receptor; E2, 17b-estradiol; ERE-LUC, estrogen-responsive-element-containing luciferase reporter; ERa, estrogen receptor a; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; GST, glutathione S-transferase; PR, progesterone receptor; PRMT2, arginine N-methyltransferase 2.

Molecular basis underlying histone H3 lysine–arginine methylation pattern readout by Spin/Ssty repeats of Spindlin1

“…Intriguingly, Spindlin1 and PRMT2 are both overexpressed in many human malignant tumors Zhong et al 2012). Given the oncogenic and Wntprompting activity of Spindlin1, disruption of the methyl pattern readout of Spindlin1 may open a new avenue for cancer therapeutics (Jiang et al 2008;Ying and Tao 2009).…”

PRMT8 demonstrates variant-specific expression in cancer cells and correlates with patient survival in breast, ovarian and gastric cancer

“…varied tissue-specific effects may be due to expression of different PRMT8 transcript variants, as the probe set data were not variant-specific, preventing uncoupling of the effects of specific PRMT8 transcript variants on patient survival. The present study believes that this possibility merits future investigation into the use of variant-specific PRMT8 expression as a cancer biomarker; much in the same way that variant-specific expression of PRMT1 has been explored (3,(14)(15)(16). It is worth noting that, even in the absence of available data to uncouple variant-specific PRMT8 expression and correlation with patient survival, the potential for total PRMT8 expression to be used as a prognostic biomarker and for consideration as a possible therapeutic target stands on its own.…”

“…Correlations of PRMT expression with oncogenic disease states, and the activity of PRMT family members in cancer cell phenotypes, have been previously studied, generally and in isoform-specific manners (3,(14)(15)(16). This is particularly true of PRMT1, the PRMT family member most homologous to PRMT8 (13), the expression of which is amplified in numerous breast cancer tissues and has been demonstrated to correlate with patient age, tumor grade and menopausal status (2,3).…”

“…Particular PRMT protein isoforms have been investigated in order to determine the specific roles of their protein products in cancer, suggesting the possibility for the use of PRMT transcript variants as cancer biomarkers (3,(14)(15)(16). Our previous study (17) demonstrated the endogenous expression of a novel transcript variant of PRMT8 in long-lived, fibroblast growth factor 2 (FGF2)-treated primary human dermal fibroblasts cultured in low oxygen.…”

Plant PRMTs Broaden the Scope of Arginine Methylation

“…PRMT2 was found to be coactivator of androgen (Meyer et al, 2007) and estrogen receptors (Qi et al, 2002). Recent studies in mammals demonstrated that PRMT2 is involved in pulmonary function, inflammatory response (Dalloneau et al, 2011), progression of apoptosis (Ganesh et al, 2006), breast cancer (Zhong et al, 2012), and Wnt (Blythe et al, 2010) and leptin signaling (Iwasaki et al, 2010). Higher plants, for example, dicot Arabidopsis and monocot rice, do not encode PRMT2 homolog which might has evolved in multicellular animals for animals-only functions that is evident from the tissuespecific expression of this gene in animals (Scott et al, 1998).…”