BioProject

The Spt4-Spt5 complex, and its human homolog DSIF (DRB sensitivity-inducing factor), is unique in its ability to regulate Pol II processivity. More...

The Spt4-Spt5 complex, and its human homolog DSIF (DRB sensitivity-inducing factor), is unique in its ability to regulate Pol II processivity. Previous studies have shown that Spt5 has the characteristics of a general transcription-elongation factor. However, mutagenesis of Spt5 showed specific phenotypes during development, which were far less severe than those of Pol II defects or TBP deficient embryos. It seems paradoxical that a mutation which alters a general elongation factor can cause rather specific developmental defects. By using Spt5 knockdown zebrafish embryos and microarrays, here we showed that transcript abundance for only a small subset of genes is altered by loss of 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. Thus, this study shows that gene activation levels may create different requirements for Pol II processivity. Active transcription requires Spt5 for efficient elongation through its stimulatory activity on Pol II processivity. Keywords: Spt5, microarray analysis, development, transcription, transcription elongation Overall design: The expression pattern of Spt5 knockdown embryos was compared to that of the control mopholino oligo injected embryos, both at 21 hours post-fertilization, to show the targets of Spt5. The activation levels of the Spt5-knockdown affected genes were measured by compareing the abundance of transcripts in 21 hours post-fertilization untreated embryos to that in 5 hours post-fertilization untreated embryos. Less...