scholarly journals Protein-DNA Interactions at the Opossum Npt2a Promoter are Dependent upon NHERF-1

2016 ◽  
Vol 39 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Barbara J. Clark ◽  
Rebecca D. Murray ◽  
Sarah A. Salyer ◽  
Samuel C. Tyagi ◽  
Cibi Arumugam ◽  
...  
Keyword(s):  
Complex Formation ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Proximal Promoter ◽  
Mrna Levels ◽  
Dna Interactions ◽  
Phosphate Homeostasis ◽  
Protein Levels ◽  
Protein Dna Interactions ◽  
Mrna Half Life

Background/Aims: Phosphate homeostasis is controlled by the renal reabsorption of Pi by the type IIa sodium phosphate cotransporter, Npt2a, which is localized in the proximal tubule brush border membrane. Regulation of Npt2a expression is a key control point to maintain phosphate homeostasis with most studies focused on regulating protein levels in the brush border membrane. Molecular mechanisms that control Npt2a mRNA, however, remain to be defined. We have reported that Npt2a mRNA and protein levels correlate directly with the expression of the Na+/H+ exchanger regulatory factor 1 (NHERF-1) using opossum kidney (OK) cells and the NHERF-1-deficient OK-H cells. The goal of this study was to determine whether NHERF-1 contributes to transcriptional and/or post-transcriptional mechanisms controlling Npt2a mRNA levels. Methods: Npt2a mRNA half-life was compared between OK and NHERF-1 deficient OK-H cell lines. oNpt2a promoter-reporter gene assays and electrophoretic mobility shift assays (EMSA) were used identify a NHERF-1 responsive region within the oNpt2a proximal promoter. Results: Npt2a mRNA half-life is the same in OK and OK-H cells. The NHERF-1 responsive region lies within the proximal promoter in a region that contains a highly conserved CAATT box and G-rich element. Specific protein-DNA complex formation with the CAATT element is altered by the absence of NHERF-1 (OK v OK-H EMSA) although NHERF-1 does not directly contribute to complex formation. Conclusion: NHERF-1 helps maintain steady-state Npt2a mRNA levels in OK cells through indirect mechanisms that help promote protein-DNA interactions at the Npt2a proximal promoter.

scholarly journals Site-Directed Mutagenesis Studies of Tn5 Transposase Residues Involved in Synaptic Complex Formation

2007 ◽  
Vol 189 (20) ◽  
pp. 7436-7441 ◽  
Author(s):  
Soheila Vaezeslami ◽  
Rachel Sterling ◽  
William S. Reznikoff
Keyword(s):  
Complex Formation ◽  
Catalytic Reactions ◽  
Site Directed Mutagenesis ◽  
Dna Interactions ◽  
Synaptic Complex ◽  
Biochemical Assays ◽  
Protein Dna Interactions ◽  
End Sequences ◽  
Tn5 Transposase ◽  
Cocrystal Structure

ABSTRACT Transposition (the movement of discrete segments of DNA, resulting in rearrangement of genomic DNA) initiates when transposase forms a dimeric DNA-protein synaptic complex with transposon DNA end sequences. The synaptic complex is a prerequisite for catalytic reactions that occur during the transposition process. The transposase-DNA interactions involved in the synaptic complex have been of great interest. Here we undertook a study to verify the protein-DNA interactions that lead to synapsis in the Tn5 system. Specifically, we studied (i) Arg342, Glu344, and Asn348 and (ii) Ser438, Lys439, and Ser445, which, based on the previously published cocrystal structure of Tn5 transposase bound to a precleaved transposon end sequence, make cis and trans contacts with transposon end sequence DNA, respectively. By using genetic and biochemical assays, we showed that in all cases except one, each of these residues plays an important role in synaptic complex formation, as predicted by the cocrystal structure.

scholarly journals Overlapping and CpG methylation-sensitive protein-DNA interactions at the histone H4 transcriptional cell cycle domain: distinctions between two human H4 gene promoters.

1992 ◽  
Vol 12 (7) ◽  
pp. 3273-3287 ◽  
Author(s):  
A J van Wijnen ◽  
F M van den Ent ◽  
J B Lian ◽  
J L Stein ◽  
G S Stein
Keyword(s):  
Cell Cycle ◽  
Transcriptional Regulation ◽  
Dna Binding ◽  
Consensus Sequence ◽  
Proximal Promoter ◽  
Gene Promoters ◽  
Histone H4 ◽  
Dna Interactions ◽  
Protein Dna Interactions ◽  
Diploid Cells

Transcriptional regulation of vertebrate histone genes during the cell cycle is mediated by several factors interacting with a series of cis-acting elements located in the 5' regions of these genes. The arrangement of these promoter elements is different for each gene. However, most histone H4 gene promoters contain a highly conserved sequence immediately upstream of the TATA box (H4 subtype consensus sequence), and this region in the human H4 gene FO108 is involved in cell cycle control. The sequence-specific interaction of nuclear factor HiNF-D with this key proximal promoter element of the H4-FO108 gene is cell cycle regulated in normal diploid cells (J. Holthuis, T.A. Owen, A.J. van Wijnen, K.L. Wright, A. Ramsey-Ewing, M.B. Kennedy, R. Carter, S.C. Cosenza, K.J. Soprano, J.B. Lian, J.L. Stein, and G.S. Stein, Science, 247:1454-1457, 1990). Here, we show that this region of the H4-FO108 gene represents a composite protein-DNA interaction domain for several distinct sequence-specific DNA-binding activities, including HiNF-D, HiNF-M, and HiNF-P. Factor HiNF-P is similar to H4TF-2, a DNA-binding activity that is not cell cycle regulated and that interacts with the analogous region of the H4 gene H4.A (F. LaBella and N. Heintz, Mol. Cell. Biol. 11:5825-5831, 1991). The H4.A gene fails to interact with factors HiNF-M and HiNF-D owing to two independent sets of specific nucleotide variants, indicating differences in protein-DNA interactions between these H4 genes. Cytosine methylation of a highly conserved CpG dinucleotide interferes with binding of HiNF-P/H4TF-2 to both the H4-FO108 and H4.A promoters, but no effect is observed for either HiNF-M or HiNF-D binding to the H4-FO108 gene. Thus, strong evolutionary conservation of the H4 consensus sequence may be related to combinatorial interactions involving overlapping and interdigitated recognition nucleotides for several proteins, whose activities are regulated independently. Our results also suggest molecular complexity in the transcriptional regulation of distinct human H4 genes.

scholarly journals Overlapping and CpG methylation-sensitive protein-DNA interactions at the histone H4 transcriptional cell cycle domain: distinctions between two human H4 gene promoters

1992 ◽  
Vol 12 (7) ◽  
pp. 3273-3287
Author(s):  
A J van Wijnen ◽  
F M van den Ent ◽  
J B Lian ◽  
J L Stein ◽  
G S Stein
Keyword(s):  
Cell Cycle ◽  
Transcriptional Regulation ◽  
Dna Binding ◽  
Consensus Sequence ◽  
Proximal Promoter ◽  
Gene Promoters ◽  
Histone H4 ◽  
Dna Interactions ◽  
Protein Dna Interactions ◽  
Diploid Cells

Transcriptional regulation of vertebrate histone genes during the cell cycle is mediated by several factors interacting with a series of cis-acting elements located in the 5' regions of these genes. The arrangement of these promoter elements is different for each gene. However, most histone H4 gene promoters contain a highly conserved sequence immediately upstream of the TATA box (H4 subtype consensus sequence), and this region in the human H4 gene FO108 is involved in cell cycle control. The sequence-specific interaction of nuclear factor HiNF-D with this key proximal promoter element of the H4-FO108 gene is cell cycle regulated in normal diploid cells (J. Holthuis, T.A. Owen, A.J. van Wijnen, K.L. Wright, A. Ramsey-Ewing, M.B. Kennedy, R. Carter, S.C. Cosenza, K.J. Soprano, J.B. Lian, J.L. Stein, and G.S. Stein, Science, 247:1454-1457, 1990). Here, we show that this region of the H4-FO108 gene represents a composite protein-DNA interaction domain for several distinct sequence-specific DNA-binding activities, including HiNF-D, HiNF-M, and HiNF-P. Factor HiNF-P is similar to H4TF-2, a DNA-binding activity that is not cell cycle regulated and that interacts with the analogous region of the H4 gene H4.A (F. LaBella and N. Heintz, Mol. Cell. Biol. 11:5825-5831, 1991). The H4.A gene fails to interact with factors HiNF-M and HiNF-D owing to two independent sets of specific nucleotide variants, indicating differences in protein-DNA interactions between these H4 genes. Cytosine methylation of a highly conserved CpG dinucleotide interferes with binding of HiNF-P/H4TF-2 to both the H4-FO108 and H4.A promoters, but no effect is observed for either HiNF-M or HiNF-D binding to the H4-FO108 gene. Thus, strong evolutionary conservation of the H4 consensus sequence may be related to combinatorial interactions involving overlapping and interdigitated recognition nucleotides for several proteins, whose activities are regulated independently. Our results also suggest molecular complexity in the transcriptional regulation of distinct human H4 genes.

Ontogenic regulation of folate transport across rat jejunal brush-border membrane

2003 ◽  
Vol 285 (5) ◽  
pp. G1068-G1073 ◽  
Author(s):  
Krishnaswamy Balamurugan ◽  
Hamid M. Said
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Maximum Velocity ◽  
Initial Step ◽  
Mrna Levels ◽  
Folate Transport ◽  
Adult Rats ◽  
Physiological Concentration ◽  
Adult Rat ◽  
Weanling Rats

Folate is an essential micronutrient that in mammals must be obtained from exogenous sources via intestinal absorption. Previous studies from our laboratory and others have demonstrated that folate absorption from the small intestine is mediated via the reduced-folate carrier (RFC). The goal of this study was to determine whether the initial step of folate uptake by intestinal epithelial cells, i.e., transport across the brush-border membrane (BBM) of the polarized enterocytes, is ontogenically regulated, and if so, to determine the molecular mechanism involved. Purified BBM vesicles (BBMV) isolated from suckling, weanling, and adult rats were used in this study. The initial rate of carrier-mediated uptake of a physiological concentration of folic acid (0.1 μM) by jejunal BBMV was found to be significantly ( P < 0.01) higher in suckling compared with weanling rats, which was, in turn, significantly ( P < 0.01) higher than that in adult rats. This decline in carrier-mediated folate uptake with maturation was found to be mediated via a decrease in the maximum velocity of the folate uptake process (6.55 ± 0.87, 2.16 ± 0.10, 0.90 ± 0.16 pmol·mg protein-1·10 s-1 for suckling, weanling, and adult rats, respectively), with no changes in its apparent Km. Western blot analysis of BBM protein and real-time PCR showed RFC protein and mRNA levels, respectively, to be significantly ( P < 0.01 for both) higher in suckling compared with weanling rats, which were in turn significantly ( P < 0.01 for both) higher than that in adult rats. These changes were found by nuclear run-on assay to be associated with a parallel decline in the RFC transcriptional rate in jejunal epithelia with maturation. In situ hybridization showed a similar pattern of RFC message distribution along crypt/villus axis in suckling and adult rat jejunum. These results demonstrate for the first time that folate transport across the intestinal BBM is under ontogenic regulation during early stages of life and that this regulation involves a transcriptional regulatory mechanism(s).

Glucocorticoids upregulate taurocholate transport by ileal brush-border membrane

1997 ◽  
Vol 273 (1) ◽  
pp. G197-G203 ◽  
Author(s):  
M. J. Nowicki ◽  
B. L. Shneider ◽  
J. M. Paul ◽  
J. E. Heubi
Keyword(s):  
Steady State ◽  
Bile Acid ◽  
Western Blot ◽  
Brush Border ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Initial Velocity ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Mrna Levels

The regulation of the enterohepatic circulation of bile acids has not been fully elucidated. Substrate availability has been shown to have a regulatory role on the ileal uptake of taurocholate (TC) by a positive feedback mechanism. Other mechanisms are likely to be involved in regulating ileal bile acid uptake. The present study was designed to test the hypothesis that the ileal bile acid transporter (iBAT) is glucocorticoid sensitive and that changes in expression are mediated by changes in iBAT synthesis. Adult Sprague-Dawley rats (300–400 g) received intraperitoneal injections with either corticosterone (5 mg/ 100 g body weight) or an equivalent vehicle (control) daily for 3 days. On day 4, ileal brush-border membrane vesicles (BBMV) and hepatic basolateral membrane vesicles (BLMV) were prepared, and TC transport was performed using the rapid filtration technique. Initial velocity was measured at selected time points, and kinetics were calculated over a range of TC concentrations. Ileal RNA was isolated, and Northern analysis of steady-state iBAT mRNA levels was determined. Western blot analysis was performed to quantitate the level of the 48-kDa iBAT protein. The initial velocity of Na(+)-dependent TC uptake at 30 s by ileal BBMV was higher in treated animals (264.3 +/- 64.6 pmol/mg protein) compared with control animals (148.3 +/- 41.1 pmol/mg protein; P = 0.07). The maximal velocity of uptake (Vmax) was significantly higher in treated vs. control animals (1,091 +/- 62.7 vs. 689.1 +/- 55.0 pmol.min-1.mg protein-1, respectively; P = 0.002), whereas there was no significant difference in the Michaelis constant (Km) between the control and treated animals (43.3 +/- 7.2 vs. 35.3 +/- 8.7 microM, respectively; P = not significant). Steady-state iBAT mRNA levels were increased twofold in the treated vs. control groups. Western blot analysis showed that the abundance of the 48-kDa iBAT protein was eightfold higher in the treated animals compared with control. Kinetic analysis of hepatic Na(+)-dependent TC uptake revealed nearly identical Vmax and Km between the study and control animals. Therefore, we conclude that TC transport by ileal BBMV is upregulated by administration of glucocorticoids. The increase in BBMV transport Vmax corresponds to an increase in both iBAT transcript and protein.

Expression of intestinal brush-border membrane hydrolases and ferritin after segmental ischemia-reperfusion in rats

1998 ◽  
Vol 275 (3) ◽  
pp. G572-G583 ◽  
Author(s):  
Kwo-Yih Yeh ◽  
Mary Yeh ◽  
Jonathan Glass
Keyword(s):  
Internal Control ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Protein Complexes ◽  
Ischemia Reperfusion ◽  
Binding Activity ◽  
Mrna Levels ◽  
Intestinal Alkaline Phosphatase ◽  
Protein Activity ◽  
Mobility Shift

Jejunal expression of three brush-border membrane (BBM) enzymes, intestinal alkaline phosphatase (IAP), lactose-phlorizin hydrolase (LPH), and sucrase-isomaltase (SI), and a cytosolic protein, ferritin (Ft), was investigated after transient segmental ischemia-reperfusion (I/R). I/R reduced mucosal IAP, LPH, and SI mRNAs to 36%, 11%, and 38% of normal jejunal levels after 3 h of reperfusion and to 22%, 8%, and 51% of normal jejunal levels after 6 h of reperfusion, respectively. Intriguingly, in the internal control jejunum IAP and LPH mRNAs also decreased significantly. LPH and SI mRNA rapidly recovered to levels significantly higher than those of normal jejunum at 12 h, whereas IAP mRNA levels did not recover until 48 h. Enzyme activity paralleled changes in mRNA levels in the ischemic reperfused jejunum. Electrophoretic mobility shift assays showed that I/R significantly increased SI footprinting 1 (SIF1) binding activity. The mobility of one of the DNA-protein complexes was further retarded in the presence of anti-Cdx-2 antibody, suggesting that either Cdx-2 or a related protein was interacting with the SIF1 sequences. Similar to BBM enzymes, cytosolic Ft mRNA and protein were significantly decreased at 3 and 6 h after I/R. By 12 h, Ft mRNA, but not Ft protein, had increased to higher than normal levels. We conclude that a rapid recovery of BBM mRNAs and enzymes occurs in regenerating mucosa after upper villus damage. The increase of SIF1 binding protein activity after I/R may enhance SI, and perhaps LPH, gene transcription. The expression of Ft is regulated at both pretranslational and translational levels.

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