【原文参考】Previous studies demonstrate that the regulation of gene transcription by nuclear receptors is mainly due to the realization that not only the interaction of the receptors with DNA, but also that many transcription co-regulators (including both co-activators and co-repressors), which were crucial in transmitting the signals to the transcriptional machinery of the receptors。

【修改参考】Previous studies demonstrate that the regulation of gene transcription by nuclear receptors is mainly due to not only the realization of  the interaction of the receptors with DNA, but also  many transcription co-regulators (including both co-activators and co-repressors), which were crucial in transmitting the signals to the transcriptional machinery of the receptors.

【参考译文】早先的研究显示，核受体对基因转录的调节作用不仅主要归因于其（核受体）与核酸相互作用的实现，而且归因于大量的辅调控因子，而正是这些辅调控因子在把信号传递到核受体的转录系统中起到关键作用。

【参考解析】

1.原文中的that很显然想要表达一种同位关系，但是我觉得应该用of来表达。至于that有无这种用法还真不清楚；

2.感觉not only 的位置也使用不当。

由于专业关系只能提供这么多分析，就这还参考了搞理工科专业翻译朋友的意见，仅供参考吧。我查了下原文，很可能是我们中国人的杰作。