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

在真核生物的细胞核中，DNA形成高度折叠的染色质，这是不活跃的转录。高迁移率基团（High mobility group， HMG）蛋白具有包括阳离子dna结合域和阴离子区域的特征结构，可以使染色质结构松动以促进转录。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将被放松。高度致密的染色质随后会松动以减少扭曲，可能是为了促进转录因子的作用。为了证明这一假设，我们合成了水溶性多两性电解质，一种含有氨基酸和羧酸悬吊体（PEG- ac）的聚乙二醇（PEG）衍生物，以及一种具有精胺侧链的透明质酸（HA） （Spn-HA），并研究了它们对染色质的转录刺激作用。与这些多两性水解物孵育的染色质明显提高了转录效率，转录率比原始染色质高9-17倍。DNA/多阳离子复合物的转录效率也明显提高。荧光恢复和各向异性测量证实了这些多两性电解质对DNA复合物的松动作用。这些结果将揭示HMG蛋白诱导转录激活的一种新的生理机制。这些合成的多两性水解物有望作为人工HMG蛋白模型和基因转染改善剂。

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.