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.

Promotion and regulation of ribosomal transcription in eukaryotes by RNA polymerase I.

Abstract: Publisher Summary This chapter discusses the mechanisms of eukaryotic ribosomal transcription and its regulation. Ribosomal transcription has been studied in an exceptionally wide range of organisms. In eukaryotes, ribosomal gene transcription uses a dedicated set of transcription factors and a specialized ribonucleic acid (RNA) polymerase, the deoxyribonucleic acid (DNA)-dependent RNA polymerase I (RPOI). The resultant precursor-rRNA (pre-rRNA) is neither capped nor polyadenylated and is produced in the nucleolus; a large nuclear structure visible in the light microscope. Moreover, the promotion of ribosomal transcription is generally directed, by a 100- to 150-bp DNA sequence that lies across and, predominantly, upstream of the transcription-initiation site. Promotion requires an activated form of RPOI, the DNA-binding factor upstream transcription factor (UBF), and the TATA binding protein (TBP) I -complex, containing three TATA-box binding protein associated protein (TAF) I s. Upstream binding factor (UBF) binds to both an upstream and an initiation-site promoter element, probably coiling the promoter into a 180-bp loop. This allows the interaction of the TBP,-complex, and subsequent polymerase recruitment. The activity of the promoter is enhanced by a promoter-proximal terminator, by enhancer repeats in the proximal IGS, and by the presence in the IGS of duplicate spacer promoters. Further upstream, other sequences may also modulate transcription.

A yeast protein that influences the chromatin structure of UASG and functions as a powerful auxiliary gene activator.

Abstract: GRF2, an abundant yeast protein of Mr -127,000, binds to the GAL upstream activating sequence (UASc) and creates a nucleosome-free region of -230 bp. Purified GRF2 binds to sequences found in many other UASs, in the 35S rRNA enhancer, at centromeres, and at telomeres. Although GRF2 stimulates transcription only slightly on its own, it combines with a neighboring weak activator to give as much as a 170-fold enhancement. This effect of GRF2 is strongly distance-dependent, declining by 85% when 22 bp is interposed between the GRF2 and neighboring activator sites.

Binding of a nuclear factor to a regulatory sequence in the promoter of the mouse H-2Kb class I major histocompatibility gene.

Abstract: A cis-acting regulatory sequence was identified upstream of the mouse H-2Kb class I major histocompatibility gene. Deletions in the H-2Kb promoter revealed that sequences located between 190 and 138 nucleotides upstream of the transcription initiation site contribute to basal gene expression as well as to stimulation by alpha-interferon. Furthermore, a nuclear factor found in several cell types binds with high affinity to a sequence centered 166 nucleotides upstream of the H-2Kb initiation site. In vivo competition experiments demonstrated that this factor plays a direct role in H-2Kb expression in mouse fibroblasts. The binding site for this factor is TGGGGATTCCCCA, a sequence of perfect dyad symmetry. This factor also binds a similar sequence in the 72-base-pair repeat enhancer element of simian virus 40.

Transcriptional "silencer" element in rat repetitive sequences associated with the rat insulin 1 gene locus.

Abstract: The enhancer elements from either simian virus 40 or murine sarcoma virus activate the expression of a transfected rat insulin 1 (rI1) gene when placed within 2.0 kilobases or less of the rI1 gene cap site. Inclusion of 4.0 kilobases of upstream rI1 sequence, however, results in a substantial reduction in the enhancer-dependent insulin gene expression. These observations suggested that a negative transcriptional regulatory element was present between 2.0 and 4.0 kilobases of the rI1 sequence. To test this notion, we employed a heterologous enhancer-dependent transcription assay in which the simian virus 40 72-base-pair repeat is linked to a human beta-globin gene. Addition of the upstream rI1 element to this system decreased the level of enhancer-dependent beta-globin transcription by a factor of 5 to 15. This rI1 "silencer" element functions in a manner relatively independent of position and orientation and requires a cis-dependent relationship to the transcription unit on which it acts. Thus, the silencer sequence seems to have a number of the characteristics of enhancer elements, and we suggest that it may function by the converse of the enhancer mechanism. The rI1 silencer sequence was identified as a member of a long interspersed rat repetitive family. Thus, a potential role for certain repetitive sequences interspersed throughout the eukaryotic genome may be to regulate gene expression by retaining transcriptional activity within defined domains.