Bio-compatible gene-delivery systems with transcriptional-enhancing function

在真核细胞核中，DNA形成高度折叠的染色质，其不被主动转录。高迁移率族（HMG）蛋白具有包含阳离子DNA结合结构域和阴离子区域的特征结构，已知其使染色质结构松散以促进转录。两性结构是激活转录所必需的，但其机制尚不清楚，两性HMG蛋白与DNA结合，同时与组蛋白相互作用，DNA与组蛋白之间的强结合会被松弛。高度致密的染色质会被松开以减少扭曲，可能是为了促进转录因子的接近。具有氨基和羧酸侧基的（乙二醇）（PEG）衍生物（PEG-AC），和具有精胺侧链的透明质酸（HA）（Spn-HA），结果表明，这些两性聚电解质与染色质共孵育后，其转录效率明显提高，比原染色质的转录效率提高了9-17倍。这些两性聚电解质也明显提高了DNA/聚阳离子复合物的转录效率。荧光恢复和各向异性测量证实了两性聚电解质对DNA复合物的致松作用，这些结果为HMG蛋白诱导转录激活提供了一种新的生理机制。这些合成的两性聚电解质有望作为人工HMG蛋白模型，也是基因转染促进剂。

In eukaryotic nuclei, DNA forms highly folded chromatin which is not actively transcribed. High mobility group (HMG) proteins, having characteristic structures comprising both cationic DNA-binding domains and an anionic region, are known to loosen the chromatin structure to facilitate the transcription. Amphoteric structure is necessary to activate the transcription, though its mechanism is still not clear.The amphoteric HMG protein binds to DNA, simultaneously interacting with histones, and the strong binding between DNA and histones would be relaxed. Highly compacted chromatin would then be loosened to reduce the distortion, presumably to promote the approach of transcription factors.To prove the hypothesis, we synthesized water-soluble polyampholytes, a poly(ethylene glycol) (PEG) derivative bearing both amino- and carboxylic acid-pendants (PEG-AC), and a hyaluronic acid (HA) having spermine side chains (Spn-HA), and their transcription-stimulating effect on the chromatin was examined.Incubation of chromatin with these polyampholytes evidently enhanced the transcriptional efficiency, and 9-17 times higher transcriptional rate than the original chromatin was observed. Transcription efficiency of DNA/polycation complexes was also obviously improved by these polyampholyte. Loosening of the DNA complexes by these polyampholytes was confirmed by the fluorescent restoration and anisotropy measurements.These results would show a novel physiological mechanism of HMG protein-induced transcriptional activation. These synthetic polyampholytes are expected as an artificial HMG protein model, and also a gene transfection improver.