The Std1 protein modulates the expression of glucose-regulated genes, but its exact molecular role in this process is unclear. A two-hybrid screen for Std1-interacting proteins identified the hydrophilic C-terminal domains of the glucose sensors, Snf3 and Rgt2. The homologue of Std1, Mth1, behaves differently from Std1 in this assay by interacting with Snf3 but not Rgt2. Genetic interactions between STD1, MTH1, SNF3, and RGT2 suggest that the glucose signaling is mediated, at least in part, through interactions of the products of these four genes. Mutations in MTH1 can suppress the raffinose growth defect of a snf3 mutant as well as the glucose fermentation defect present in cells lacking both glucose sensors (snf3 rgt2). Genetic suppression by mutations in MTH1 is likely to be due to the increased and unregulated expression of hexose transporter genes. In media lacking glucose or with low levels of glucose, the hexose transporter genes are subject to repression by a mechanism that requires the Std1 and Mth1 proteins. An additional mechanism for glucose sensing must exist since a strain lacking all four genes (snf3 rgt2 std1 mth1) is still able to regulate SUC2 gene expression in response to changes in glucose concentration. Finally, studies with green fluorescent protein fusions indicate that Std1 is localized to the cell periphery and the cell nucleus, supporting the idea that it may transduce signals from the plasma membrane to the nucleus.
We characterized rice cDNA sequences for OsDr1 and OsDrAp1 , which encode structural homologs of the eukaryotic general repressors Dr1 and DrAp1, respectively. OsDr1 and OsDrAp1 are nuclear proteins that interact with each other and with the TATA binding protein/DNA complex. In vitro and in vivo functional analyses showed that OsDrAp1 functions as a repressor, unlike its role in other eukaryotic systems, in which DrAp1 is a corepressor. OsDr1 and OsDrAp1 functioned together as a much stronger repressor than either one alone. Functional dissections revealed that the N-terminal histone-fold domains of OsDr1 and OsDrAp1 were necessary and sufficient for their repression and proteinprotein interaction with each other. The unique glutamine-and proline-rich domain of OsDr1 had no repression activity. The basic amino acid-rich region and an arginine and glycine repeat domain of OsDrAp1 enhanced its repression activity. Thus, although OsDr1 and OsDrAp1 function as repressors, the functions of the two components are reversed compared with those of their nonplant counterparts. INTRODUCTIONSuccessful plant growth, development, and response to environmental cues require precise control of gene expression. A key control stage of differential gene expression is transcriptional regulation mediated by transcriptional factors. Studies of plant transcription factors have focused mainly on activators (Schwechheimer et al., 1998;Riechmann et al., 2000), whereas repressors have just begun to receive attention.Several transcriptional repressors have been cloned from plants, and the elucidation of their functional mechanisms has begun. Transcriptional repressors have been found to mediate plant hormone signal transduction. For example, the soybean G box binding factor 2 (SGBF-2) is a basic leucine zipper (bZIP)-type factor that binds to the G box of the auxin response element of the GH3 promoter and represses both basal and auxin-induced transcription of a reporter gene (Liu et al., 1997). In Arabidopsis, auxin response factor 1 (ARF1) binds to the auxin response element TGTCTC and functions as a repressor (Ulmasov et al., 1999). Arabidopsis ethylene-responsive element binding factors 3 and 4 (AtERF3 and AtERF4) interact with the ethylene-responsive element (GCC box) and repress the basal activity of a reporter gene and the activity of the transcription activator AtERF5 (Fujimoto et al., 2000). Tobacco ERF3 (NtERF3) also functions as a GCC box-dependent transcriptional repressor. The C-terminal 35 amino acids of NtERF3, which contains the conserved L/FDLNL/F(X)P motif, are sufficient to confer the capacity for transcriptional repression on a heterologous DNA binding domain (Ohta et al., 2001). A developmentspecific transcriptional repressor gene, ROM2 , has been cloned from French bean. ROM2 is a bZIP-type transcription factor that functions as a DNA binding site-dependent repressor. ROM2 represses PvALF-activated transcription of the promoter of phytohemagglutinin ( DLEC2 ). The expression analysis indicates that the ROM2 repressor m...
Bdellovibrio bacteriovorus 109J is an obligate intraperiplasmic predator of other Gram-negative bacteria. Collision with a suitable prey cell initiates a developmental sequence ultimately resulting in the destruction of the prey cell and the production of progeny bdellovibrios. Two-dimensional gel analysis of patterns of protein synthesis at various times in a synchronously growing culture of Bdellovibrio bacteriovorus 109J revealed over 30 polypeptides whose syntheses are developmentally regulated. The majority of these polypeptides fall into nine categories: attack phase specific or one of eight different kinetic groups expressed during the intraperiplasmic growth phase. The results indicate that Bdellovibrio bacteriovorus 109J has a complex system for regulating gene expression during its developmental cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.