PubMed Health⌕ Search

Biomedical subjects

J R Greene

Publications and source records attributed to J R Greene.

9 recordsLinked to original sources
PubMed1992

Parallel pathways of gene regulation: homologous regulators SWI5 and ACE2 differentially control transcription of HO and chitinase.

Two independent pathways of transcriptional regulation that show functional homology have been identified in yeast. It has been demonstrated previously that SWI5 encodes a zinc finger DNA-binding protein whose transcription and cellular localization both are cell cycle regulated. We show that ACE2, whose zinc finger region is nearly identical to that of SWI5, shows patterns of cell cycle-regulated transcription and nuclear localization similar to those seen previously for SWI5. Despite their similarities, SWI5 and ACE2 function in separate pathways of transcriptional regulation. SWI5 is a transcriptional activator of the HO endonuclease gene, whereas ACE2 is not. In contrast, ACE2 is a transcriptional activator of the CTS1 gene (which encodes chitinase), whereas SWI5 is not. An additional parallel between the SWI5/HO pathway and the ACE2/CTS1 pathway is that HO and CTS1 both are cell cycle regulated in the same way, and HO and CTS1 both require the SWI4 and SWI6 transcriptional activators. Overproduction of either SWI5 or ACE2 permits transcriptional activation of the target gene from the other pathway, suggesting that the DNA-binding proteins are capable of binding in vivo to promoters that they do not usually activate. Chimeric SWI5/ACE2 protein fusion experiments suggest that promoter specificity resides in a domain distinct from the zinc finger domain.

Amino Acid Sequence↗
PubMed1991

Bacteriophage SPO1 middle transcripts.

Phage SPO1 middle transcripts are known to fall into two classes, m and m1l. Class m1l transcripts continue to be made late in the viral infection, while the synthesis of class m transcripts ceases soon after the onset of replication and late transcription. The experiments that are reported here deal with the regulatory nature of this diversity. The accumulation of transcripts associated with eight middle promoters was analyzed by S1 nuclease mapping. DNA sequence surrounding these middle promoters was determined or redetermined, and the stability of RNA associated with most of these promoters was also analyzed. Class m1l transcription was shown to be associated with SPO1 middle promoters that remain active at late stages of viral development, when middle promoters of class m are repressed. The consensus sequences of class m and m1l middle promoters were found to be indistinguishable and the search for sequences consensual with late promoters yielded only divergent candidates. No other consensus sequence that is specific and exclusive to either class of middle promoters was detected within a hundred base pairs upstream or downstream of these promoters. Considerable variations in the stabilities of SPO1 middle transcripts were found. Two promoters that are only 71 base pairs apart yielded transcripts that had substantially different stabilities. The 5'-flanking segment of the transcript associated with the upstream promoter apparently conferred a high degree of stability on this RNA.

Bacillus subtilis↗
PubMed1987

Subcloning.

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed1986

DNA binding by the bacteriophage SPO1-encoded type II DNA-binding protein, transcription factor 1. Formation of nested complexes at a selective binding site.

The interactions of the phage SPO1-encoded Type II DNA-binding protein, transcription factor 1 (TF1), with one of its preferred binding sites in SPO1 DNA have been analyzed in detail. The results suggest that TF1 recognizes a high-affinity "core" binding site and that additional protein moieties can accrue to either side of the occupied core site to form higher order complexes. Close contacts between TF1 and the core binding site as well as some of the steric requirements for recognition of the core site were determined. Comparison of the nucleotide sequences of several preferred binding sites for TF1 reveals a striking lack of precise homology but does show common features.

Bacteriophages↗
PubMed1986

DNA binding by the bacteriophage SPO1-encoded type II DNA-binding protein, transcription factor 1. Site-specific binding requires 5-hydroxymethyluracil-containing DNA.

The bacteriophage SPO1-encoded Type II DNA-binding protein, transcription factor 1 (TF1), forms complexes with specific sites in SPO1 DNA. We have investigated the binding of TF1 to one of its preferred sites in which the normal 5-hydroxymethyluracil (hmUra) of SPO1 DNA has been replaced by thymine and have also investigated the binding of a bacterial Type II DNA-binding protein (from Bacillus stearothermophilus) to the hmUra- and thymine-containing forms of the same DNA segment. Our results show that TF1 binds selectively to this high affinity binding site only in hmUra-containing DNA and that the bacterial Type II DNA-binding protein interacts nonspecifically with both forms of DNA.

Binding Sites↗
PubMed1986

The phage SPO1-specific RNA polymerase, E.gp28, recognizes its cognate promoters in thymine-containing DNA.

The bacteriophage SPO1 gene 28-encoded protein, gp28, directs specific recognition of viral middle promoters in hydroxymethyluracil-containing DNA by the Bacillus subtilis host's RNA polymerase core. Using appropriately sensitive methods of detection, we have shown that discrimination against thymine-containing DNA is not absolute and that the gp28-containing RNA polymerase precisely initiates transcription at two thymine-containing SPO1 middle promoters.

Bacteriophages↗
PubMed1986

Synergistic toxicity of endotoxin and hemoglobin.

Stroma-free hemoglobin (SFH) is advocated as an oxygen-transporting resuscitation solution. Hemoglobin has been shown to enhance endotoxin lethality when given intraperitoneally. It is possible that SFH could interact with endotoxin when used as an oxygen-transporting resuscitation system for trauma victims with contaminating wounds. To assess the effects of these two agents when given intravascularly, rabbits were infused with SFH (1.75 gm/kg) or albumin (controls; 1.75 gm/kg) with and without endotoxin. Two doses of endotoxin were used. At 14.5 ng/kg of Salmonella enteritidis endotoxin, no effect was seen in the albumin group. However, 50% of the hemoglobin group died. At 14.5 micrograms/kg, the albumin group showed hematologic alterations, but all animals lived. All SFH-treated animals died at the higher endotoxin dose. SFH alone caused cardiac abnormalities (bradycardia in 100%, sinus arrhythmias in 30%, and ventricular arrhythmias in 20%), liver abnormalities (necrosis in 40% and 240% increase in alanine aminotransferase activity by 6 hours), and intravascular thrombi (30%). The only hemoglobin-induced abnormality that was more frequent in the presence of endotoxin was ventricular arrhythmias (up to 75% of animals). Thrombin times were approximately 20% larger in all SFH groups compared with the albumin groups. By 6 hours after infusion, endotoxin prolonged the thrombin time even further, despite the lack of fibrinogen consumption. This study shows that endotoxin and SFH exert synergistic toxicity when SFH is given in a clinically relevant dose for an oxygen-transporting resuscitation system. Only minute quantities of endotoxin are needed to produce this phenomenon. We hypothesize that this synergism is endotoxin enhancement of hemoglobin toxicity.

Animals↗
PubMed1986

Toxicity of human hemoglobin solution infused into rabbits.

Aqueous human hemoglobin is being considered as an oxygen-transporting resuscitation solution. However, there are some indications that such solutions may be toxic. We report here that at a clinically significant dose (20% to 30% of the estimated blood volume) of hemoglobin solution (10 gm/dl), toxicity similar to that reported in humans is produced in rabbits. This toxicity is characterized by cardiac rhythm disturbances (25%) and coagulation abnormalities, manifested as intravascular thrombi. Hypoxia, tissue necrosis (brain 29%, liver 25%), and death (22%) were seen. Hypoxia appears to be the cause of death, because the arterial PO2 of rabbits that died was significantly lower (43 +/- 8 mm Hg) than that of rabbits that lived (80 +/- 12 mm Hg). We also report the effect of the method of preparation or degree of purity on the observed toxicity. Stroma-free red blood cell hemolysate, stroma-free hemoglobin, zinc-precipitated hemoglobin, and chromatographically purified hemoglobin were infused. Purification of these solutions ranged from removal of stroma to removal of all detectable nonhemoglobin protein components. In addition, the nonhemoglobin proteins were concentrated and infused into rabbits to compare their effects. All of these hemoglobin solutions induced similar toxicity for rabbits infused with stroma-free hemoglobin. The nonhemoglobin proteins, as well as human serum albumin, exhibited no toxicity. These results demonstrate that, at the clinically relevant dose, hemoglobin or something inherently associated with hemoglobin is toxic.

Animals↗