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.

Regulation of phospholipid biosynthesis by phosphatidylinositol transfer protein Sec14p and its homologues. A critical role for phosphatidic acid.

Abstract: Transcription of yeast phospholipid biosynthesis structural genes, which contain an inositol-sensitive upstream activating sequence in their promoters, responds to the availability of the soluble precursors inositol and choline and to changes in phospholipid metabolism. The INO1 gene is deregulated (derepressed when inositol is present) under the conditions of increased phosphatidylcholine (PtdCho) turnover, as occurs in the sec14Δ cki1Δ strain (SEC14 encodes the major yeast phosphatidylinositol transfer protein; CKI1 encodes choline kinase of the cytidine diphosphate choline pathway of PtdCho biosynthesis). Five proteins (Sfhp) share sequence homology with phosphatidylinositol transfer protein Sec14p. Two (Sfh2p and Sfh4p), when overexpressed largely complement the otherwise essential Sec14p requirement concerning growth and secretion. In this study, we analysed the ability of Sec14 homologues to correct the defect in regulation of phospholipid biosynthesis resulting from defective or missing Sec14p. We also analysed how PtdCho turnover relates to the transcriptional regulation of phospholipid biosynthesis. The results show that (a) none of the Sec14 homologues was able to substitute for Sec14p in its regulatory aspects of phospholipid biosynthesis, (b) removal of phospholipase D activity corrected the aberrant INO1 gene regulation in yeast strains with otherwise high PtdCho turnover, and (c) increased steady-state phosphatidic acid levels correlated with derepressed levels of the INO1 gene. Overall, the results support the model in which high phosphatidic acid levels lead to derepression of the genes of phospholipid biosynthesis [Henry, S.A. & Patton-Vogt, J.L. (1998) Prog. Nucleic Acid Res. Mol. Biol.61, 133–179].

Synergistic activation of eukaryotic gene transcription by multiple upstream sites

Abstract: Sigmoid curve and non additive activation by multiple regulatory sites are two typical manifestations of transcriptional synergy in eukaryotes. There are three possible mechanisms for synergistic regulation: interaction between activators, cooperative binding of activators to DNA upstream sites and cooperative interaction of site bound activators with GTM (general transcriptional machinery) components. All these mechanisms involve direct or indirect interactions among multiple activators that bind to upstream regulatory sites. The pre bound activators can facilitate the binding of free ones through these interactions and this underlines the basis of synergistic activation.

Expression of Arabidopsis LINEs from two promoters.

Abstract: Most Arabidopsis long interspersed elements (LINEs, called ATLNs) have two open reading frames, orf1 and orf2. In the 5' untranslated regions (UTRs) located upstream of orf1, the most proximal segments of tens of base pairs long are not homologous even in two ATLN members with almost identical sequences. In this study, we first show that RT-PCR products from ATLN39, a member of ATLN, can be detected only in total RNA from the hypomethylation mutant ddm1 or from suspension-cultured cells treated with a DNA methylation inhibitor 5-azacytidine, indicating that the expression of ATLN39 is negatively regulated by DNA methylation. We then show that orf1 fused in frame with the luciferase (luc) gene is expressed in suspension-cultured cells of A. thaliana when the 5' UTR is present in the region upstream of orf1. Analysis of deletion in the 5' UTR revealed that the 5' UTR has two promoters, designated here as P1 and P2. Analysis of transcripts by 5' RACE showed that their 5' ends were located at sites immediately upstream of the P1 region or at sites downstream of the P2 region. This observation and the fact that the P1 region contains no TATA sequence indicate that P1 is an internal promoter that initiates transcription from sites upstream of the promoter. A sequence containing GGCGA with a CpG methylatable site is conserved in the P1 regions in members closely related to ATLN39. The P2 region, however, contains the TATA sequence as well as another sequence with a CpG site. The TATA sequence is conserved in members closely related to ATLN39 but not in the other ATLN members, suggesting that P2 is the promoter uniquely present in the ATLN39-related members. Transcripts from promoter P1 can be used as templates to give new copies proficient in retroposition, but those from promoter P2 cannot because of the lack of the proximal half region of the 5' UTR sequence. Transcripts from promoter P2, as well as those from promoter P1 can, however, be used for the production of a sufficient amount of proteins for retroposition. Only a short sequence of the non-homologous region is present at the 5' ends of transcripts from promoter P1, thus suggesting that the non-homologous regions seen in the most proximal regions in ATLN elements are not generated in transcription.