• BMB Reports
• /
• 제37권6호
• /
• pp.709-714
• /
• 2004

The wild-type repressor CI of temperate mycobacteriophage L1 and the temperature-sensitive (ts) repressor CIts391 of a mutant L1 phage, L1cIts391, have been separately overexpressed in E. coli. Both these repressors were observed to specifically bind with the same cognate operator DNA. The operator-binding activity of CIts391 was shown to differ significantly than that of the CI at 32 to $42^{\circ}C$. While 40-95% operator-binding activity was shown to be retained at 35 to $42^{\circ}C$ in CI, more than 75% operator-binding activity was lost in CIts391 at 35 to $38^{\circ}C$, although the latter showed only 10% less binding compared to that of the former at $32^{\circ}C$. The CIts391 showed almost no binding at $42^{\circ}C$. An in vivo study showed that the CI repressor inhibited the growth of a clear plaque former mutant of the L1 phage more strongly than that of the CIts391 repressor at both 32 and $42^{\circ}C$. The half-life of the CIts391-operator complex was found to be about 8 times less than that of the CI-operator complex at $32^{\circ}C$. Interestingly, the repressor-operator complexes preformed at $0^{\circ}C$ have shown varying degrees of resistance to dissociation at the temperatures which inhibit the formation of these complexes are inhibited. The CI repressor, but not that of CIts391, regains most of the DNA-binding activity on cooling to $32^{\circ}C$ after preincubation at 42 to $52^{\circ}C$. All these data suggest that the 131st proline residue at the C-terminal half of CI, which changed to leucine in the CIts391, plays a crucial role in binding the L1 repressor to the cognate operator DNA, although the helix-turn-helix DNA-binding motif of the L1 repressor is located at its N-terminal end.

• Bulletin of the Korean Chemical Society
• /
• 제24권5호
• /
• pp.579-582
• /
• 2003

Norfloxacin, that inhibits the action of topoisomerase Ⅱ, binds to wide variety of DNA. The binding mode of this drug to double- and super-coiled DNA (ds- and scDNA) is compared in this study by various spectroscopic methods, including absorption, fluorescence, and circular dichroism(CD) spectroscopy. Hypochromism in the absorption band, negative and positive induced CD bands (respectively in 240-260 nm and 270-300 nm region) are apparent for the norfloxacin that bound to both the dsDNA and scDNA. A decrease in fluorescence is also noticed in the presence of both DNAs. Since the spectroscopic characteristics are the same for both complexes, it is imperative that the binding mode of the norfloxacin is similar in ds- and scDNA. In the presence of $Mg^{2+}$, which is a cofactor in the topoisomerase Ⅱ action, the fluorescence intensity of the scDNA-norfloxacin complex increased and the resulting fluorescence intensity and shape was identical to that in the absence of scDNA. Therefore, the addition of an excess amount of $Mg^{2+}$ may result in the extrusion of norfloxacin from scDNA.

• Animal cells and systems
• /
• 제7권1호
• /
• pp.81-87
• /
• 2003

While screening proteins that interact with DnaA protein, the initiator protein for Escherichia coil chromosomal DNA replication, we found a 52-kD sized protein which bound to DnaA protein in a salt-dependent manner. This protein was identified as trigger factor, a ribosome-associated peptidyl-prolyl- cisltrans isomerase with chaperone activity. Trigger factor was overproduced and purified to near homogeneity, and its effect on the function of DnaA protein was examined, Enhanced binding of DnaA protein to DnaA box with no apparent supershift in the gel-shift experiments suggested that trigger factor, by virtue of its chaperone activity, exerts a change on DnaA protein thus increasing its binding affinity for DnaA box.

• Asian-Australasian Journal of Animal Sciences
• /
• 제14권6호
• /
• pp.771-776
• /
• 2001

A pregnant-induced clone was identified by differential screening from a cDNA library of bovine mammary gland. The clone was identified as a cDNA encoding a polyadenylate binding protein 1 (PABP). The cDNA clone had a total length of 1,911 nucleotides coding for 636 amino acids. The nucleotide sequence of the bovine PABP was 95% and 94% identical to those of human and mouse species, respectively. Comparison of the deduced amino acid sequences of bovine PABP with those of human species showed 100% identity. Induction of the PABP mRNA was observed in bovine mammary tissues at pregnant 7 and 8 months compared to virgin, lactating and involuted states. Expression of the PABP gene was examined in mammary epithelial HC11 cells at proliferating, differentiated and apoptotic conditions. The mRNA levels of PABP gene were similar between proliferating and differentiated cells, but expression levels were very low in apoptotic cells compared to other conditions. Results demonstrate that the PABP gene is induced during pregnancy at which stage mammary epithelial cells are actively proliferating.

• Archives of Pharmacal Research
• /
• 제24권1호
• /
• pp.55-63
• /
• 2001

Aucubin, an irdoid g1ucoside, was investigated to determine whether it has a stimulating effect on $\alpha$-amanitin excretion in $\alpha$-amanitin intoxicated rats, and whether there is binding activity to calf thymus DNA. High-performance liquid chromatography (HPLC) analysis of $\alpha$-amanitin in rat urine allowed quantitative measurement of the $\alpha$-amanitin concentration with a detection limit of 50${mu}g/ml$. In this system, a group treated with both $\alpha$-amanitin and aucubin showed that o(-amanitin was excreted about 1.4 times faster than in the $\alpha$-amanitin only treated group. Our previous results showed that the toxicity of $\alpha$-amanitin is due to specific inhibition of RNA polymerase activity and the resultant blockage of the synthesis of certain RNA species in the nucleus. However, no significant activity change on RNA polymerase from Hep G2 cells was observed when aucubin was treated with $\alpha$-amanitin at any concentration tested. Nevertheless, aucubigenin inhibited both DNA polymerase (IC50, 80.5${mu}g/ml$) and RNA polymerase (IC50, 135.0${mu}g/ml$) from the Hep G2 cells. The potential of both $\alpha$-amanitin and aucubin to interact with DNA were examined by spectrophotometric analysis. $\alpha$-Amanitin showed no significant binding capacity to calf thymus DNA, but aucubin was found to interact with DNA, and the apparent binding constant ($K_{app}$) and apparent number of binding sites per D7A phosphate ($B_{app}$) were 0.45$0.45{\times}$$10^4$ $M^{-1}$ and 1.25, respectively.

• BMB Reports
• /
• 제38권4호
• /
• pp.474-480
• /
• 2005

Curcumin, a major active component of turmeric, has been identified as an inhibitor of the transcriptional activity of activator protein-1 (AP-1). Recently, it was also found that curcumin and synthetic curcumin derivatives can inhibit the binding of Jun-Fos, which are the members of the AP-1 family, to DNA. However, the mechanism of this inhibition by curcumin and its derivatives was not disclosed. Since the binding of Jun-Fos dimer to DNA can be modulated by redox control involving conserved cysteine residues, we studied whether curcumin and its derivatives inhibit Jun-Fos DNA binding activity via these residues. However, the inhibitory mechanism of curcumin and its derivatives, unlike that of other Jun-Fos inhibitors, was found to be independent of these conserved cysteine residues. In addition, we investigated whether curcumin derivatives can inhibit AP-1 transcriptional activity in vivo using a luciferase assay. We found that, among the curcumin derivatives examined, only inhibitors shown to inhibit the binding of Jun-Fos to DNA by Electrophoretic Mobility Shift Assay (EMSA) inhibited AP-1 transcriptional activity in vivo. Moreover, RT-PCR revealed that curcumin derivatives, like curcumin, downregulated c-jun mRNA in JB6 cells. These results suggest that the suppression of the formation of DNA-Jun-Fos complex is the main cause of reduced AP-1 transcriptional activity by curcuminoids, and that EMSA is a suitable tool for identifying inhibitors of transcriptional activation.

• Journal of Microbiology and Biotechnology
• /
• 제9권5호
• /
• pp.562-567
• /
• 1999

Single-stranded DNA binding protein (SSB) is well-characterized as having a helix-destabilizing activity. The helix-destabilizing capability of SSB has been re-examined in this study. The results of restriction endonuclease protection assays and titration experiments suggest that the stimulatory effect of SSB on strand exchange acts by melting out the secondary structure which is inaccessible to RecA protein binding; however, SSB is excluded from regions of secondary structure present in native single-stranded DNA. Complexes of SSB and RecA protein are required for eliminating the secondary structure barriers under optimal conditions for strand exchange.

• 한국미생물학회:학술대회논문집
• /
• 한국미생물학회 2002년도 추계학술대회
• /
• pp.135-139
• /
• 2002

Yeast cells respond to condition of amino acid starvation by synthesizing GCN4, a typical eukaryotic transcriptional activator, which regulates the expression of many amino acids biosynthetic genes. By introducing point mutations in the DNA binding domain of GCN4, mutants with normal DNA binding activity but defective in transcriptional activity were isolated to identify unknown proteins that could suppress the mutant phenotype under an amino acid depletion condition. As a result, SSB(Stress-Seventy B) subfamily proteins were identified as suppressors of mutant GCN4. SSB proteins were known as a member of yeast hsp70 family that probably aids passage of nascent chain through ribosomes. Among them, the mechanism of suppression by SSB2 on the defective GCN4 mutant strains is under investigation. Gcn4p directly interacts with Ssb2p through the basic DNA binding domain of GCN4. It suggests the possibility that physical interaction might induce the transcriptional activation of Gcn4p.

• Molecules and Cells
• /
• 제21권3호
• /
• pp.376-380
• /
• 2006

Gene expression is regulated in large part at the level of transcription under the control of sequence-specific transcriptional regulatory proteins. Therefore, the ability to affect gene expression at will using sequencespecific artificial transcription factors would provide researchers with a powerful tool for biotechnology research and drug discovery. Previously, we isolated 56 novel sequence-specific DNA-binding domains from the human genome by in vivo selection. We hypothesized that these domains might be more useful for regulating gene expression in higher eukaryotic cells than those selected in vitro using phage display. However, an unpredictable factor, termed the "context effect", is associated with the construction of novel zinc finger transcription factors--- DNA-binding proteins that bind specifically to 9-base pair target sequences. In this study, we directly selected active artificial zinc finger proteins from a zinc finger protein library. Direct in vivo selection of constituents of a zinc finger protein library may be an efficient method for isolating multi-finger DNA binding proteins while avoiding the context effect.

• Tuberculosis and Respiratory Diseases
• /
• 제42권6호
• /
• pp.801-812
• /
• 1995

CR asthma is associated with disease chronicity, a positive family history of asthma and in vitro and in vivo defects in mononuclear cell function. The HPA axis in CR asthmatics is suppressed normally by dexamethasone and the pharmacokinetic profile of an oral dose of prednisolone is similar to that found in CS subjects. In addition, competitive binding studies have shown that the ligand binding and nuclear translocation functions of the GR are similar in the two groups. Studies using gel retardation assay have indicated a defect in DNA binding in CR subjects. Chemical mutational analysis of the GR has shown that is not due to a defect in its structure at the cDNA level. Scatchard analysis of the GR/DNA and GR/ligand interactions suggests that there may be transcriptional interference of the GR with other transcriptionally active molecules leading to defective gene transcription.