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Upstream activating sequence

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An upstream activation sequence (UAS) is a cis-acting regulatory sequence. It is distinct from the promoter and increases the expression of a neighbouring gene. Due to its essential role in activating transcription, the upstream activating sequence is often considered to be analogous to the function of the enhancer in multicellular eukaryotes.[1]

Examples of Upstream Activation Sequences in Research

GAL1-GAL10 Intergenic Region

Several studies have been conducted with Saccharomyces cerevisiae to explore the exact function of upstream activation sequences, often focusing on the GAL1-GAL10 intergenic region [1]. Its property to bind the GAL4 protein is utilised in the GAL4/UAS technique for controlled gene misexpression in Drosophila. In this technique, four related binding sites between the GAL10 and GAL1 loci in Saccharomyces cerevisiae serve as an Upstream Activating Sequences (UAS) element through GAL4 binding.[2].

One study explored the galactose-responsive upstream activation sequence (UASG),looking at the influence of proximity to this UAS for nucleosome positioning. Proximity to the UAS was chosen because deletions of DNA flanking the UAS left the nucleosome array unaltered, indicating that nucleosome positioning was not related to sequence-specific histone-DNA interactions. The role of specific regions of UASG was analyzed by inserting oligonucleotides with different binding properties, leading to the successful identification of a region responsible for the creation of an ordered array. It should be noted that the sequence identified overlapped a binding site for GAL4 protein, which is a positive regulator for transcription which coincides with the function of upstream activating sequences. t[3].

Another study looked at the effect of inserting the UASG into the promoter region of the glyceraldehyde-3-phosphate dehydrogenase gene (GPD). This hybrid promoter was then utilized to express human immune interferon, a toxic substance to yeast that results in a reduced copy number and low plasmid stability. Relative to the native promoter, expression of the hybrid promoter was induced roughly 150- to 200-fold in the cultures by growth in galactose, induction that wasn't apparent with glucose as the carbon source. When compared to the native GPD promoter, the presence of UASG caused the transcriptional activity to remain equivalently enhanced under induced conditions.[4]

References

  1. ^ Webster, Nocholas; Jin, Jia Rui; Green, Stephen; Hollis, Melvyn; Chambon, Pierre (29 January 1988). "The Yeast UASG is a transciptional enhancer in human hela cells in the presence of the GAL4 trans-activator". Cell. 52 (2): 169–178.
  2. ^ Duffy, Joseph B. (2002). "GAL4 system in Drosophilia: A Fly Geneticist's Swiss Army Knife". Genesis. 34 (1–2): 1–15.
  3. ^ Fedor, Martha J.; Lue, Neal F.; Kornberg, Roger D. (5 November 1988). "Statistical positioning of nucleosomes by specific protein-binding to an upstream activating sequence in yeast". Journal of Molecular Biology. 204 (1): 109–127.
  4. ^ Bitter, Grant A.; Egan, Kevin M. (30 September 1988). "Expression of interferon-gamma from hybrid yeast GPD promoters containing upsream regulatory sequences from the GAL1-GAL10 intergenic region". Gene. 69 (2): 193–207.