Structure and functional analysis of a molecular switch that regulated the mRNA synthesis rate.

转录延伸因子DSIF由人Spt 4和Spt 5组成，其调节RNA聚合酶II持续合成能力的能力是独特的。用培养的HeLa细胞和体外转录测定的实验显示，DNA结合转录激活因子Ga 14 VP 16对转录的刺激依赖于人Spt 5，表明活跃转录的基因需要DSIF活性。微阵列分析显示，大约7.5%的基因通过特异性吗啉代反义介导的斑马鱼Spt 5敲低降低了它们的表达。对下调基因的进一步研究表明，在未处理的胚胎中，被敲低最强烈抑制的基因在早期发育期间被强烈激活，支持上述结果。另一方面，DSIF和转录延伸因子NELF的协同作用负调控RNA聚合酶II的转录延伸。在这项研究中，我表明DSIF和NELF有助于调节junB基因的表达不仅通过暂停RNA聚合酶II在启动子近端区域的延伸细胞因子IL-6诱导前，但也通过减弱mRNA诱导水平诱导后。此外，已分离出两个人Spt 5的缺失突变体，以阐明mRNA合成速率的调节机制。

The transcription elongation factor DSIF, which is comprised of human Spt4 and Spt5, is unique in its ability to regulate RNA polymerase II processivity. Experiments with cultured HeLa cells and in vitro transcription assays revealed that stimulation of transcription by the DNA-binding transcription activator Ga14VP16 is dependent on human Spt5, indicating that actively transcribed genes require DSIF activity. Microarray analysis revealed that approximately 7.5% of genes decreased their expression by a specific morpholino antisense-mediated knockdown of zebrafish Spt5. Further investigation of the down-regulated genes showed that the genes most intensely repressed by the knockdown were strongly activated during early development in untreated embryos, supporting above results. On the other hand, cooperative action of DSIF and the transcription elongation factor NELF negatively regulates transcription elongation by RNA polymerase II. In this study, I show that DSIF and NELF contribute to the regulation of junB gene expression not only by pausing RNA polymerase II elongation at promoter proximal region before cytokine IL-6 induction, but also by attenuating mRNA induction level after induction. In addition, two deletion mutants of human Spt5 have been isolated to elucidate the regulatory mechanisms of the mRNA synthesis rate.