Disease relevance of REB1

• AIMS: To investigate the survival and persistence of Lactobacillus plantarum REB1 in the fermentation process of liquid pig feed on a working farm in standard production conditions [1].
• Finally, although bacterial replication terminator proteins blocked yeast RNA polymerases in a polar fashion, a yeast transcription terminator protein (Reb1p) was unable to block T7 RNA polymerase and E. coli DnaB helicase [2].

High impact information on REB1

• This segment contains a binding site of the Myb-related protein Reb1 and an adjacent dT:dA tract [3].
• The transcription termination site for yeast RNA polymerase I requires not only an 11 bp binding site for Reb1p, but also about 46 bp of 5' flanking sequence [4].
• Purified GRF2 binds to sequences found in many other UASs, in the 35S rRNA enhancer, at centromeres, and at telomeres [5].
• The Tbf1 and Reb1 proteins are present in yeast subtelomeric regions [6].
• For example, tethering the N-terminal domain of Tbf1 and Reb1 in a subtelomeric region shortens that telomere proportionally to the number of domains bound [6].

Biological context of REB1

• This protein also binds to a site present in the enhancer for the 35S rRNA gene, which is transcribed by RNA polymerase I, and appears to be identical to the previously described REB1 protein (B. E. Morrow, S. P. Johnson, and J. R. Warner, J. Biol. Chem. 264:9061-9068, 1989) [7].
• When oligonucleotides containing a REB1-binding site are placed between the CYC1 upstream activating sequence and TATA box, transcription by RNA polymerase II in vivo is substantially reduced, suggesting that REB1 acts as a repressor of RNA polymerase II transcription [7].
• We show that REB1-binding sites normally situated in the SIN3 promoter and in the 35S rRNA promoter can substitute for the ILV1 REB1 site [8].
• A binding site for the yeast REB1 protein was identified near the 5' terminus of the ENO1 URS element [9].
• There was some homology between a portion of REB1 and the DNA-binding domain of the oncogene myb [10].

Associations of REB1 with chemical compounds

• A greater reduction in REB1 activity is observed if the sin3 mutant strain is grown in media containing galactose as a carbon source [7].
• The GRF2-binding factor appears to facilitate the binding of proteins to both HSE1 and TATA, as these sequences, while still occupied, are less protected from in vivo dimethyl sulfate methylation in a deltaGRF2 strain [11].
• A recombinant histidine-tagged Reb1 protein bearing the rDNA binding domain has two homologous, sequence-specific binding sites in the S. pomber DNA intergenic spacer, located between 289 and 480 nt downstream of the end of the approximately 25S rRNA coding sequences [12].
• These map to the transcription initiation site, the TATA box, the promoter-distal heat shock element (HSE1) and a consensus GRF2 (REB1/Factor Y) sequence [13].
• Previous work has shown that the DNA sequence recognized by Reb1p contains an adenosine residue that is unusually reactive toward chemical modification by dimethylsulfate and that methylation of this nucleoside increases the binding affinity of the Reb1p protein for its target [14].

Physical interactions of REB1

• The in vitro levels of the REB1 DNA-binding activity are reduced in extracts prepared from strains bearing a mutation in the SIN3 gene [7].
• The upstream repression sequence from the yeast enolase gene ENO1 is a complex regulatory element that binds multiple trans-acting factors including REB1 [9].
• Datin, a yeast poly(dA:dT)-binding protein, behaves as an activator of the wild-type ILV1 promoter and interacts synergistically with Reb1p [15].
• Surprisingly, mutation of the Reb1p binding site had no effect on nucleosome positioning or on the kinetics or extent of activation or repression of either the GAL1 or GAL10 promoters under any of the conditions assayed [16].
• A Reb1p-binding site is required for efficient activation of the yeast RAP1 gene, but multiple binding sites for Rap1p are not essential [17].

Regulatory relationships of REB1

• From this experiment, we conclude that GCR1 is able to activate gene expression in the absence of REB1 or RAP1 bound at adjacent binding sites [18].

Other interactions of REB1

• This suggests that ABF1 and REB1 may have related functions within the cell [8].
• Using in vitro and in vivo footprinting techniques, we have identified four binding sites for three factors in the 5' noncoding region of TPI: a REB1-binding site located at positions -401 to -392, two GCR1-binding sites located at positions -381 to -366 and -341 to -326, and a RAP1-binding site located at positions -358 to -346 [18].
• Concerted action of the transcriptional activators REB1, RAP1, and GCR1 in the high-level expression of the glycolytic gene TPI [18].
• In addition to Reb1p, the sequence of the Gal4p-binding site influences basal transcription [19].
• This expression requires two elements within gal1-10 sequences, a REB1-binding site and a second element, Z, which resides 20 base pairs upstream of the GCN4-binding site [20].

Analytical, diagnostic and therapeutic context of REB1

• Gel retardation assays showed that REB1 binds specifically to this element [8].
• Site-directed mutagenesis of REB1 and ABF1 binding sites demonstrated uncoupling of RNA polymerase I-dependent termination from transcriptional activation in vivo [21].
• Immunoprecipitation analysis demonstrated that REB1 is phosphorylated [22].
• We have used a random selection protocol to define the consensus and range of binding sites for the Saccharomyces cerevisiae REB1 protein [23].
• Northern blots of GCY1 transcripts confirm that Reb1p modulates basal transcription and has little influence on the galactose-induced state [24].

References