Phosphorylated proteins play important roles in the regulation of many different cell networks. However, unlike the preparation of proteins containing unmodiffed proteinogenic amino acids, which can be altered readily by site-directed mutagenesis and expressed in vitro and in vivo, the preparation of proteins phosphorylated at predetermined sites cannot be done easily and in acceptable yields. To enable the synthesis of phosphorylated proteins for in vitro studies, we have explored the use of phosphorylated amino acids in which the phosphate moiety bears a chemical protecting group, thus eliminating the negative charges that have been shown to have a negative effect on protein translation. Bis-o-nitrobenzyl protection of tyrosine phosphate enabled its incorporation into DHFR and IκB-α using wild-type ribosomes, and the elaborated proteins could subsequently be deprotected by photolysis. Also investigated in parallel was the re-engineering of the 23S rRNA of Escherichia coli, guided by the use of a phosphorylated puromycin, to identify modified ribosomes capable of incorporating unprotected phosphotyrosine into proteins from a phosphotyrosyl-tRNACUA by UAG codon suppression during in vitro translation. Selection of a library of modified ribosomal clones with phosphorylated puromycin identified six modified ribosome variants having mutations in nucleotides 2600–2605 of 23S rRNA; these had enhanced sensitivity to the phosphorylated puromycin. The six clones demonstrated some sequence homology in the region 2600–2605 and incorporated unprotected phosphotyrosine into IκB-α using a modified gene having a TAG codon in the position corresponding to amino acid 42 of the protein. The purified phosphorylated protein bound to a phosphotyrosine specific antibody and permitted NF-κB binding to a DNA duplex sequence corresponding to its binding site in the IL-2 gene promoter. Unexpectedly, phosphorylated IκB-α also mediated the exchange of exogenous DNA into an NF-κB–cellular DNA complex isolated from the nucleus of activated Jurkat cells.
Previous studies have shown that regulation of the epidermal growth factor gene (EGFR) pathway plays a role in glioma progression. Certain genotypes of the EGFR gene may be related to increased glioblastoma risk, indicating that germ line EGFR polymorphisms may have implications in carcinogenesis. To examine whether and how variants in the EGFR gene contribute to glioma susceptibility, we evaluated nine tagging single-nucleotide polymorphisms (tSNPs) of the EGFR gene in a case–control study from Xi'an city of China (301 cases, 302 controls). EGFR SNP associations analyses were performed using SPSS 16.0 statistical packages, PLINK software, Haploview software package (version 4.2) and SHEsis software platform. We identified two susceptibility tSNPs in the EGFR gene that were potentially associated with an increased risk of glioma (rs730437, p = 0.016; OR: 1.32; 95%CI: 1.05–1.66 and rs1468727, p = 0.008; OR: 1.31; 95%CI: 1.04–1.65). However, after a strict Bonferroni correction analysis was applied, the significance level of the association between EGFR tSNPs and risk of glioma was attenuated. We observed a protective effect of haplotype “AATT” of the EGFR gene, which was associated with a 29% reduction in the risk of developing glioma, while haplotype “CGTC” increased the risk of developing glioma by 36%. Our results, combined with previous studies, suggested an association between the EGFR gene and glioma development.
In this study, we have prepared a DNA-affibody nanoparticle which mimics a antibody in its ability to specifically target the HER2 receptor. This nanoparticle has a smaller size (95 kDa) than the monoclonal antibody, trastuzumab (150 kDa) and at least two-fold greater activity toward BT474 cells than trastuzumab. The DNA in this nanoparticle structure has two functions, namely as a support to anchor two affibody molecules and as a vehicle to non-covalently bind multiple copies of a small molecule drug for drug delivery. Each DNA-affibody nanoparticle can bind ∼53 molecules of doxorubicin (DOX) to form a complex, which exhibits greater selectivity toward and inhibition of breast cancer cells overexpressing HER2 than doxorubicin does. As expected, the nanoparticle exhibits lesser inhibition of cells expressing HER2 at a low level. Thus, the nanoparticle represents a highly efficacious agent for inhibiting cancer cells which overexpress HER2, but with low toxicity toward normal cells.
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