Furthermore rs is the one which is studied well so

Furthermore, rs17171119 is the one which is studied well so far. One of the earlier studies has reported the clinical outcome and impact of EZH2 SNPs (rs41277434, rs3757441, rs2302427 rs9177211 T> C) (Crea et al., 2012). The only coding SNP ID rs2302427 has been studied in various diseases such as hepatocellular carcinoma, oral carcinoma, gastric cancer, prostate cancer, lung cancer, urothelial cell carcinoma, breast cancer, cholangiocarcinoma and endometrial cancer and in most of the studies was found to be significantly associated with disease susceptibility (Bachmann et al., 2005, Yoon et al., 2010, Yu et al., 2013, Paolicchi et al., 2013, Zhou et al., 2014, Yu et al., 2014, Tao et al., 2015, Gao et al., 2015, Jung Su et al., 2015, Lee et al., 2018, Ling et al., 2018). So validation of this cSNP (rs2302427) by these reports compliments the findings of present study. Hence we planned to investigate this amino pten inhibitor change (rs2302427 D193H) at the level of protein structure and function. However, no data is available regarding the remaining 6 SNPs predicted in the present study (rs1880357, rs1996996, rs73158274, rs73158280, rs10952783, rs2177567). Thus more epidemiological and clinical studies are needed to validate the SNPs reported in the present study. EZH2 functions as an epigenetic regulator, it is known to carry out trimethylation of lysine residues of histone protein (H3K27). H3K27 is an epigenetic mark associated with transcriptional repression of various genes so as to maintain the homeostasis of differentiation and development. Overexpression of EZH2 has been reported in a number of cancers (Varambally et al., 2002; Kleer et al., 2003; Verambally et al., 2008; Wagener et al., 2010; Takawa et al., 2011). The EZH2 protein is composed of 746 amino acids but the structure is not yet resolved completely. Few studies have given the structural and functional insight of the respective protein in order to resolve its trajectory of the mechanism of action and its regulation. The EZH2 protein is known to have one to several conformations while the transition from inactive to active state and vice-versa. The active form of EZH2 is a trimer complex of EZH2/EED/SUZ12, further its trimethylation activity is enhanced upon binding of RBBP4/RBBP7 (histone-binding protein) and AEBP2 (Zn-finger protein). The SET domain lies at the C-terminus of EZH2 protein (503–725 amino acids) which has the methyltransferase activity. This domain has three parts (SET domain, I-SET and Post-SET), these three domains in conjunction provide sequence specificity and positioning of substrate (lysine peptide of histone protein) into the groove (active site) and helps in co-factor (SAM) binding when CXC domain (N-terminus domain) is present (Cao and Zhang, 2004, Margueron et al., 2009, Ernst et al., 2010, Margueron and Reinberg, 2011, Wang et al., 2013,). In the present study, we have resolved the effect of D > H change which lie at N-terminus of EZH2 protein in SANT domain (Wu et al., 2013). The SANT domain is named after-Switching defective protein 3, Adaptor 2, Nuclear receptor co-repressor and Transcription factor TFIIIB. The major function of SANT is well established. SANT domain is structurally similar to Myb protein, this domain has an affinity towards histone protein and it helps in chromatin remodeling (Boyer et al., 2004). Although EZH2 gene is widely known because of it's overexpression in various cancers, still the full native structure of EZH2 is not known in PDB. To get the native structure of the EZH2 protein, we selected the template (5HYN) with the help of protein BLAST. Asp193His lies in helix-turn-helix which is in concordance with already studied SANT domain (159–250 amino acids). The structure for native protein was modeled by I-TASSER and Modeler v9.20. Further structure modeled by Modeler v9.20 was preferred on the basis of results of Ramachandran plot and free energy calculations per residue (Figs. 5 & 6). The comparison of native and variant structure for D193H reveals the increased stability in terms of compactness, solvent accessible surface area (extent of hydrophobicity), the presence of –COOH group (extent of polarity), nature/behavior of side chain (extent of rigidity) and degree of protonation. In the case of Histidine, due to the presence of side chain in the aromatic ring structure, causes the lesser structural flexibility and increase in compactness as supported by the radius of gyration (Fig. 9). Comparison of evaluation of solvent accessibility for native as well as variant residue indicated the lesser bulkiness of the histidine, thus might be creating a lesser interactive environment for substrate and enzyme. Despite both being polar, aspartic acid have an extra –COOH which might help in more open conformation of groove in SET domain at catalytic site and hence it might be facilitating the lysine peptide entry while the variant histidine provide the depression in ionic environment surrounding the groove hence predicted to resulting in narrower groove and thus not allowing the entry of substrate (the similar mechanisms of inactivation have already been proposed by Wu et al., 2013). In addition, histidine has lesser protonation capacity than aspartic acid so the protein might have challenging issues while conformational changes.