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.

Transcription factor Oct-2A contains functionally redundant activating domains and works selectively from a promoter but not from a remote enhancer position in non-lymphoid (HeLa) cells.

Abstract: In non-lymphoid cells such as HeLa cells, ectopic expression of the lymphocyte-specific transcription factor Oct-2A can activate reporter genes whose promoters consist of a single octamer sequence (ATTTGCAT) upstream of a TATA box. While the factor is strongly active in a promoter position, it tails as an enhancer factor: an enhancer consisting of multiple copies of the octamer sequence placed downstream of the reporter gene is not active in HeLa cells, even at high concentration of Oct-2A. In B lymphoid cells, however, the same enhancer is highly active. This could mean that an additional factor is required for enhancer activation in B cells. Furthermore, we have tested the transcriptional activation potential of Oct-2A with a series of N-terminal and C-terminal deletions. We show that a glutamine-rich domain near the N-terminus is required for full activity. Otherwise, large segments of the N-terminal half or the entire C-terminal region are dispensable in our assay, as long as the deletions do not impinge on the conserved POU domain which is sufficient for DNA binding. While N-terminal and C-terminal regions can functionally compensate for each other, a combined deletion that only retains the POU domain is a strong down mutation. We also find that activity depends on the promoter structure of the reporter gene: the POU domain by itself shows some activity with a promoter where the octamer sequence is located very close to the TATA box, but no activity with another promoter construction where the octamer sequence is located further upstream. The two promoters also respond differently to the deletion of the glutamine-rich stretch important for transcriptional activation. From these experiments we consider it likely that the natural octamer factor variants can selectively activate the different naturally occurring octamer-containing promoters.

Location, structure, and function of the target of a transcriptional activator protein.

Abstract: We have isolated and characterized single-amino-acid substitution mutants of RNA polymerase a subunit defective in CAP-dependent transcription at the lac promoter but not defective in CAP-independent transcription. Our results establish that (1) amino acids 258- 265 of a constitute an "activation target" essential for CAP-dependent transcription at the lac promoter but not essential for CAP-independent transcription, (2) amino acid 261 is the most critical amino acid of the activation target, (3) amino acid 261 is distinct from the determinants for a-DNA interaction, and (4) the activation target may fold as a surface amphipathic a-helix. We propose a model for transcriptional activation at the lac promoter that integrates these and other recent results regarding transcriptional activation and RNA polymerase structure and function.

Co-ordinated regulation of amino sugar biosynthesis and degradation: the NagC repressor acts as both an activator and a repressor for the transcription of the glmUS operon and requires two separated NagC binding sites.

Abstract: The NagC repressor controls the expression of the divergently transcribed nagE-nagBACD operons involved in the uptake and degradation of the amino sugars, N-acetyl-D-glucosamine (GlcNAc) and glucosamine (GlcN). The glmUS operon, encoding proteins necessary for the synthesis of GlcN (glmS) and the formation of UDP-GlcNAc (glmU), is transcribed from two promoters located upstream of glmU. In the absence of amino sugars both promoters are active. However, in the presence of GlcNAc, the glmU proximal promoter, P1, is inactive while the upstream promoter, P2, is subject to weak induction. Two binding sites for the NagC repressor are located at -200 and -47 bp upstream of P1. Mutations which prevent NagC binding to either of these sites eliminate expression from the P1 promoter. This shows that binding of NagC is necessary for expression of the glmU P1 promoter and implies that NagC is playing the role of activator for this promoter. Moreover, the location of the distal NagC site suggests that this site is behaving like an upstream activating sequence (UAS).