Upstream activating sequence

About: Upstream activating sequence is a research topic. Over the lifetime, 1633 publications have been published within this topic receiving 100112 citations.

HLA-B locus-specific downregulation in human melanoma requires enhancer A as well as a sequence element located downstream of the transcription initiation site.

Abstract: Human MHC class I molecules are encoded by three different loci (HLA-A, -B, and -C), which are regulated at the transcriptional level through several conserved cis-acting promoter elements. The presence of locus-specific residues throughout the entire promoter region strongly suggests that the various HLA class I loci are differentially regulated. To identify regulatory sequences involved in locus-specific HLA class I gene transcription, a series of truncated HLA-A2 and HLA-B7 promoter-reporter constructs were transfected into melanoma cell lines expressing high and low levels of endogenous HLA-B, but comparable levels of HLA-A. These experiments showed that differential regulation of HLA-B expression in melanoma cell lines is mediated by a previously unidentified co-operative action of enhancer A, located 175 bp upstream of the transcription initiation site (+1), and a specific region of 20 nucleotides located at +13 to +33 bp downstream of the transcription initiation site. Furthermore, we demonstrated binding of transcription factor Yin Yang 1 to the HLA-A +13/+33 bp region, but not to the equivalent HLA-B region. Based on these results, we present a model suggesting that YY1 displaces either activating or repressing transcription factors, thereby making the HLA-A gene resistant to differential regulation.

Transcription of the folC gene encoding folylpolyglutamate synthetase-dihydrofolate synthetase in Escherichia coli.

Abstract: The folC gene of Escherichia coli is cotranscribed with an upstream gene from two promoters located in the noncoding region 5' to the coding sequence of the upstream gene. Virtually all of the expression of the folC gene product, folylpolyglutamate synthetase-dihydrofolate synthetase, is therefore due to the upstream gene promoters. No promoter activity was found in the coding sequence of the upstream gene or in the 72-base-pair noncoding region between the two genes. It is shown that a third gene, which may overlap the coding sequence of the folC gene by 8 base pairs at the 3' end, nevertheless, has an promoter independent from that of the upstream gene-folC operon. These results contrast with those presented by Nonet et al. (M. L. Nonet, C. C. Marvel, and D. Tolan, J. Biol. Chem., 262:12209-12217, 1987), who concluded that folC was cotranscribed with the gene at its 3' end and the gene upstream to folC was cotranscribed with the gene(s) further upstream. A stable stem-loop structure resembling a rho-independent terminator is present within the noncoding region between the upstream gene and the folC gene. Folypolyglutamate synthetase expression is 6- to 15-fold lower than that of the upstream gene product, suggesting that the stem-loop terminates some of the transcription from the upstream gene promoter. We found by deletion mutagenesis and cloning sequences containing the stem-loop structure into a termination reporter plasmid that this stem-loop does not act as an effective terminator of transcription. We also found that the stem-loop does not protect the upstream gene message from degradation, since expression of the upstream gene product in maxicell experiments is the same whether the stem-loop structure is present or deleted.

The US‐1 element from the gene encoding rat poly (ADP‐ribose) polymerase binds the transcription factor Sp1

Abstract: By comparing the upstream DNA sequence of the rat and human genes encoding poly(ADP-ribose) polymerase (PARP), we have defined a 16-bp conserved region and designated it as US-1 for ‘upstream sequence 1′. This element is homologous to the recently described binding site for the transcription factor Sp1 in the promoter sequence of the mouse p12 gene which encodes a protease inhibitor. Analyses in gel mobility shift assays revealed that a nuclear protein, produced by all tissue-culture cells tested, specifically binds the US-1 element. The pattern of shifted DNA · protein complexes obtained was strikingly similar to that for Sp1, which is supported by the positive displacement of these complexes by an oligomer containing the Sp1 binding site in gel shift competition experiments. Replacement of the Sp1 binding site from the basal promoter of the mouse p12 gene by the rPARP US-1 element did not result in any significant variations in the level of expression of the chloramphenicol acetyltransferase (CAT) reporter gene upon transient transfection of tissue-culture cells. However, when point mutations are introduced in the US-1 element in a similar substitution experiment, a significant reduction in CAT gene expression could be observed. These data are consistent with Sp1 interacting with the US1 element. Results from DNase I footprinting experiments clearly indicated that purified Sp1 not only binds to the US-1 element but also to four other closely located cis-acting sites scattered in the promoter of the rat PARP gene, therefore suggesting that Sp1 is likely to modulate strongly the expression of that gene in different tissues.

A Synthetic Oxygen Sensor for Plants Based on Animal Hypoxia Signaling.

Abstract: Due to the involvement of oxygen in many essential metabolic reactions, all living organisms have developed molecular systems that allow adaptive physiological and metabolic transitions depending on oxygen availability. In mammals, the expression of hypoxia-response genes is controlled by the heterodimeric Hypoxia-Inducible Factor. The activity of this transcriptional regulator is linked mainly to the oxygen-dependent hydroxylation of conserved proline residues in its α-subunit, carried out by prolyl-hydroxylases, and subsequent ubiquitination via the E3 ligase von Hippel-Lindau tumor suppressor, which targets Hypoxia-Inducible Factor-α to the proteasome. By exploiting bioengineered versions of this mammalian oxygen sensor, we designed and optimized a synthetic device that drives gene expression in an oxygen-dependent fashion in plants. Transient assays in Arabidopsis (Arabidopsis thaliana) mesophyll protoplasts indicated that a combination of the yeast Gal4/upstream activating sequence system and the mammalian oxygen sensor machinery can be used effectively to engineer a modular, oxygen-inducible transcriptional regulator. This synthetic device also was shown to be selectively controlled by oxygen in whole plants when its components were expressed stably in Arabidopsis seedlings. We envision the exploitation of our genetically encoded controllers to generate plants able to switch gene expression selectively depending on oxygen availability, thereby providing a proof of concept for the potential of synthetic biology to assist agricultural practices in environments with variable oxygen provision.