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Dooner, HK, Weil CF.  2007.  Give-and-take: interactions between DNA transposons and their host plant genomes. Curr. Opin. Genet. Dev.. 17:486–492. AbstractWebsite
Recent genome sequencing efforts have revealed how extensively transposable elements (TEs) have contributed to the shaping of present day plant genomes. DNA transposons associate preferentially with the euchromatic or genic component of plant genomes and have had the opportunity to interact intimately with the genes of the plant host. These interactions have resulted in TEs acquiring host sequences, forming chimeric genes through exon shuffling, replacing regulatory sequences, mobilizing genes around the genome, and contributing genes to the host. The close interaction of transposons with genes has also led to the evolution of intricate cellular mechanisms for silencing transposon activity. Transposons have thus become important subjects of study in understanding epigenetic regulation and, in cases where transposons have amplified to high numbers, how to escape that regulation.
Dooner, HK, He L.  2014.  Polarized gene conversion at the bz locus of maize.. Proc Natl Acad Sci USA. 111(38):13918-23. Abstract
Nucleotide diversity is greater in maize than in most organisms studied to date, so allelic pairs in a hybrid tend to be highly polymorphic. Most recombination events between such pairs of maize polymorphic alleles are crossovers. However, intragenic recombination events not associated with flanking marker exchange, corresponding to noncrossover gene conversions, predominate between alleles derived from the same progenitor. In these dimorphic heterozygotes, the two alleles differ only at the two mutant sites between which recombination is being measured. To investigate whether gene conversion at the bz locus is polarized, two large diallel crossing matrices involving mutant sites spread across the bz gene were performed and more than 2,500 intragenic recombinants were scored. In both diallels, around 90% of recombinants could be accounted for by gene conversion. Furthermore, conversion exhibited a striking polarity, with sites located within 150 bp of the start and stop codons converting more frequently than sites located in the middle of the gene. The implications of these findings are discussed with reference to recent data from genome-wide studies in other plants.
Dorsett, D, Eissenberg JC, Misulovin Z, Martens A, Redding B, McKim K.  2005.  Effects of sister chromatid cohesion proteins on cut gene expression during wing development in Drosophila. Development. 132:4743-53.Website
Doubilet, S, McKim KS.  2007.  Spindle assembly in the oocytes of mouse and Drosophila--similar solutions to a problem. Chromosome Res. 15:681-96.Website
Druzhinin, SY, Tran NT, Skalenko KS, Goldman SR, Knoblauch JG, Dove SL, Nickels BE.  2015.  A Conserved Pattern of Primer-Dependent Transcription Initiation in Escherichia coli and Vibrio cholerae Revealed by 5' RNA-seq. PLoS Genet. 11(7):e1005348.
Du, C., Fefelova, N., Caronna, J., He, L., Dooner HK.  2009.  The polychromatic Helitron landscape of the maize genome. Proc. Natl. Acad. Sci. U.S.A.. 106:19916–19921. Abstract
150 copies of a transposon-like sequence, termed Heltir, that has terminal inverted repeats resembling Helitron 3' termini. Nonautonomous Helitrons make up at least 2% of the maize genome and most of those tested show +/- polymorphisms among modern inbred lines.
Du, C, Swigonova Z, Messing J.  2006.  Retrotranspositions in orthologous regions of closely related grass species. BMC evolutionary biology. 6:62. AbstractWebsite
BACKGROUND: Retrotransposons are commonly occurring eukaryotic transposable elements (TEs). Among these, long terminal repeat (LTR) retrotransposons are the most abundant TEs and can comprise 50-90% of the genome in higher plants. By comparing the orthologous chromosomal regions of closely related species, the effects of TEs on the evolution of plant genomes can be studied in detail. RESULTS: Here, we compared the composition and organization of TEs within five orthologous chromosomal regions among three grass species: maize, sorghum, and rice. We identified a total of 132 full or fragmented LTR retrotransposons in these regions. As a percentage of the total cumulative sequence in each species, LTR retrotransposons occupy 45.1% of the maize, 21.1% of the rice, and 3.7% of the sorghum regions. The most common elements in the maize retrotransposon-rich regions are the copia-like retrotransposons with 39% and the gypsy-like retrotransposons with 37%. Using the contiguous sequence of the orthologous regions, we detected 108 retrotransposons with intact target duplication sites and both LTR termini. Here, we show that 74% of these elements inserted into their host genome less than 1 million years ago and that many retroelements expanded in size by the insertion of other sequences. These inserts were predominantly other retroelements, however, several of them were also fragmented genes. Unforeseen was the finding of intact genes embedded within LTR retrotransposons. CONCLUSION: Although the abundance of retroelements between maize and rice is consistent with their different genome sizes of 2,364 and 389 Mb respectively, the content of retrotransposons in sorghum (790 Mb) is surprisingly low. In all three species, retrotransposition is a very recent activity relative to their speciation. While it was known that genes re-insert into non-orthologous positions of plant genomes, they appear to re-insert also within retrotransposons, potentially providing an important role for retrotransposons in the evolution of gene function.
Du, C., Caronna J, He L, Dooner HK.  2008.  Computational prediction and molecular confirmation of Helitron transposons in the maize genome. BMC Genomics. 9:51. AbstractWebsite
Helitrons represent a new class of transposable elements recently uncovered in plants and animals. One remarkable feature of Helitrons is their ability to capture gene sequences, which makes them of considerable potential evolutionary importance. However, because Helitrons lack the typical structural features of other DNA transposable elements, identifying them is a challenge. Currently, most researchers identify Helitrons manually by comparing sequences. With the maize whole genome sequencing project underway, an automated computational Helitron searching tool is needed. The characterization of Helitron activities in maize needs to be addressed in order to better understand the impact of Helitrons on the organization of the genome.\\ We developed and implemented a heuristic searching algorithm in PERL for identifying Helitrons. Our HelitronFinder program will (i) take FASTA-formatted DNA sequences as input and identify the hairpin looping patterns, and (ii) exploit the consensus 5' and 3' end sequences of known Helitrons to identify putative ends. We randomly selected five predicted Helitrons from the program's high quality output for molecular verification. Four out of the five predicted Helitrons were confirmed by PCR assays and DNA sequencing in different maize inbred lines. The HelitronFinder program identified two head-to-head dissimilar Helitrons in a maize BAC sequence.\\ We have identified 140 new Helitron candidates in maize with our computational tool HelitronFinder by searching maize DNA sequences currently available in GenBank. Four out of five candidates were confirmed to be real by empirical methods, thus validating the predictions of HelitronFinder. Additional points to emerge from our study are that Helitrons do not always insert at an AT dinucleotide in the host sequences, that they can insert immediately adjacent to an existing Helitron, and that their movement may cause changes in the flanking region, such as deletions.
Duax, WL, Griffin JF, Ebright R.  1985.  Structural basis for chemotherapeutic action of antiestrogens.. Progress in clinical and biological research. 172B:263-73.
Dudas, B, Jenes B, Kiss GB, Maliga P.  2012.  Spectinomycin resistance mutations in the rrn16 gene are new plastid markers in Medicago sativa. Theor. Appl. Genet. 125:1517-23. AbstractWebsite
We report here the isolation of spectinomycin-resistant mutants in cultured cells of Medicago sativa line RegenSY-T2. Spectinomycin induces bleaching of cultured alfalfa cells due to inhibition of protein synthesis on the prokaryotic type 70S plastid ribosomes. Spontaneous mutants resistant to spectinomycin bleaching were identified by their ability to form green shoots on plant regeneration medium containing selective spectinomycin concentrations in the range of 25-50 mg/l. Sequencing of the plastid rrn16 gene revealed that spectinomycin resistance is due to mutations in a conserved stem structure of the 16S rRNA. Resistant plants transferred to the greenhouse developed normally and produced spectinomycin-resistant seed progeny. In light of their absence in soybean, a related leguminous plant, the isolation of spectinomycin-resistant mutants in M. sativa was unexpected. The new mutations are useful for the study of plastid inheritance, as demonstrated by detection of predominantly paternal plastid inheritance in the RegenSY-T2 x Szapko57 cross, and can be used as selective markers in plastid transformation vectors to obtain cisgenic plants.
Dumoulin, P, Ebright RH, Knegtel R, Kaptein R, Granger-Schnarr M, Schnarr M.  1996.  Structure of the LexA repressor-DNA complex probed by affinity cleavage and affinity photo-cross-linking.. Biochemistry. 35(14):4279-86. Abstract
The structure of the complex of full-length Escherichia coli LexA repressor with a consensus operator DNA fragment has been probed by affinity photo-cross-linking and affinity cleavage. These methods allow the determination of approximate intermolecular distances between a given protein residue and a base or sugar moiety within the operator. In a first step unique cysteine residues were introduced in positions 7, 28, 38, or 52 of the protein. In all four cases, the original amino acid was an arginine. The four amino acids in these positions were expected to be situated on the surface of LexA interacting with DNA, as inferred from the structure of the LexA DNA binding domain [Fogh et al. (1994) EMBO J. 13, 3936-3944]. In a second step, these unique cysteine side chains of the purified proteins were chemically modified either with 4-azidophenacyl bromide or with S-(2-pyridylthio)cysteaminyl-EDTA. The first set of derivatives gives rise to UV-induced cross-linking which may be revealed by alkali/heat treatment; the second leads to direct DNA cleavage in the proximity of the derivatized amino acid. To reduce hydroxyl radical diffusion, the EDTA-iron cleavage reactions were done in the presence of high amounts of glycerol. The results indicate that amino acids 7 and 52 are near nucleotide pairs 8-12 of the operator and that amino acids 28 and 36 of LexA are near nucleotide pairs 5-8 of the operator. The results unambiguously define the orientation of the LexA DNA binding domain relative to the operator and provide support for the model of the LexA-operator complex proposed by Knegtel et al. [(1995) Proteins 21, 226-236]. Ethylation interference experiments further suggest that Arg-7 contacts the phosphate group between nucleotides 8 and 9 as predicted by the model.
Durbak, AR, Phillips KA, Pike S, O'Neill MA, Mares J, Gallavotti A, Malcomber S, Gassmann W, McSteen P.  2014.  Transport of boron by the tassel-less1 aquaporin is critical for vegetative and reproductive development in maize. Plant Cell. (26):2978-2995. AbstractWebsite
The element boron (B) is an essential plant micronutrient, and B deficiency results in significant crop losses worldwide. The maize (Zea mays) tassel-less1 (tls1) mutant has defects in vegetative and inflorescence development, comparable to the effects of B deficiency. Positional cloning revealed that tls1 encodes a protein in the aquaporin family co-orthologous to known B channel proteins in other species. Transport assays show that the TLS1 protein facilitates the movement of B and water into Xenopus laevis oocytes. B content is reduced in tls1 mutants, and application of B rescues the mutant phenotype, indicating that the TLS1 protein facilitates the movement of B in planta. B is required to cross-link the pectic polysaccharide rhamnogalacturonan II (RG-II) in the cell wall, and the percentage of RG-II dimers is reduced in tls1 inflorescences, indicating that the defects may result from altered cell wall properties. Plants heterozygous for both tls1 and rotten ear (rte), the proposed B efflux transporter, exhibit a dosage-dependent defect in inflorescence development under B-limited conditions, indicating that both TLS1 and RTE function in the same biological processes. Together, our data provide evidence that TLS1 is a B transport facilitator in maize, highlighting the importance of B homeostasis in meristem function.
Durst, R, Peal DS, deVlaming A, Leyne M, Talkowski M, Perrocheau M, Simpson C, Jett C, Stone MR, Charles F et al..  2015.  Mutations in DCHS1 Cause Mitral Valve Prolapse. Nature. :inpress.
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Ebright, RH, Gunasekera A, Zhang XP, Kunkel TA, Krakow JS.  1990.  Lysine 188 of the catabolite gene activator protein (CAP) plays no role in specificity at base pair 7 of the DNA half site.. Nucleic acids research. 18(6):1457-64. Abstract
Two similar, but not identical, models have been proposed for the amino acid-base pair contacts in the CAP-DNA complex ('model I,' Weber, I. and Steitz, T., Proc. Natl. Acad. Sci. USA, 81, 3973-3977, 1984; 'model II,' Ebright, et al., Proc. Natl. Acad. Sci. USA, 81, 7274-7278, 1984). The most important difference between the two models involves Lys188 of CAP. Model I predicts that Lys188 of CAP makes a specificity determining contact with base pair 7 of the DNA half site. In contrast, model II predicts that Lys188 makes no contact with base pair 7 of the DNA half site. In the present work, we have used site-directed mutagenesis to replace Lys188 of CAP by Asn, an amino acid unable to make the putative contact. We have assessed the specificities of the following proteins, both in vitro and in vivo: wild-type CAP, [Asn188]CAP, [Val181]CAP, and [Val181;Asn188]CAP. The results indicate that Lys188 makes no contribution to specificity at base pair 7 of the DNA half site. We propose, contrary to model I, that Lys188 makes no contact with base pair 7 of the DNA half site.
Ebright, RH, Busby S.  1995.  The Escherichia coli RNA polymerase alpha subunit: structure and function.. Current opinion in genetics & development. 5(2):197-203. Abstract
Recent work has established that the Escherichia coli RNA polymerase alpha subunit consists of an amino-terminal domain containing determinants for interaction with the remainder of RNA polymerase, a carboxy-terminal domain containing determinants for interaction with DNA and interaction with transcriptional activator proteins, and a 13-36 amino acid unstructured and/or flexible linker. These findings suggest a simple, integrated model for the mechanism of involvement of alpha in promoter recognition and transcriptional activation.
Ebright, RH.  2000.  RNA polymerase: structural similarities between bacterial RNA polymerase and eukaryotic RNA polymerase II.. Journal of molecular biology. 304(5):687-98. Abstract
Bacterial RNA polymerase and eukaryotic RNA polymerase II exhibit striking structural similarities, including similarities in overall structure, relative positions of subunits, relative positions of functional determinants, and structures and folding topologies of subunits. These structural similarities are paralleled by similarities in mechanisms of interaction with DNA.
Ebright, RH, Wong JR, Chen LB.  1986.  Binding of 2-hydroxybenzo(a)pyrene to estrogen receptors in rat cytosol.. Cancer research. 46(5):2349-51. Abstract
The potent carcinogen 2-hydroxybenzo(a)pyrene (2-OH-BP) competes for binding to the estrogen receptor in the cytosol of rat uterus and liver. The dissociation constant (K1) for this interaction is congruent to 2 X 10(-5) M. In contrast, 4-hydroxybenzo(a)pyrene does not bind to the estrogen receptor; 1-hydroxybenzo(a)pyrene, 5-hydroxybenzo(a)pyrene, 6-hydroxybenzo(a)pyrene, and 12-hydroxybenzo(a)pyrene bind less tightly than does 2-OH-BP. These five chemicals are not carcinogenic. We suggest that the estrogen receptor may mediate the carcinogenic effect of 2-OH-BP or of related chemicals. One possibility is that the receptor might convey 2-OH-BP to specific sites in DNA.
Ebright, R, Dong Q, Messing J.  1992.  Corrected nucleotide sequence of M13mp18 gene III.. Gene. 114(1):81-3. Abstract
There are seven differences between the actual nucleotide (nt) sequence of bacteriophage M13mp18 gene III and the previously reported nt sequence (which had been compiled based on the nt sequence of wild-type bacteriophage M13 gene III).
Ebright, RH, Le Grice SF, Miller JP, Krakow JS.  1985.  Analogs of cyclic AMP that elicit the biochemically defined conformational change in catabolite gene activator protein (CAP) but do not stimulate binding to DNA.. Journal of molecular biology. 182(1):91-107. Abstract
We have measured the effects on catabolite gene activator protein (CAP) of 22 synthetic analogs of cAMP. Each analog was assayed to test three parameters: (1) binding to CAP; (2) induction of the conformational change in CAP; and (3) activation of transcription. Thus we have identified seven cAMP analogs that bind to CAP as well or better than does cAMP, cause the assayed conformational change in CAP, yet exhibit no ability to activate transcription. We designate these analogs class D. The conformational change elicited in CAP by the class D analogs was further investigated by: (1) sensitivity to the proteolytic enzymes chymotrypsin, Staphylococcus aureus V8 protease, subtilisin and trypsin; (2) formation of inter-subunit covalent crosslinks by 5,5'-dithiobis(2-nitrobenzoic acid); and (3) degree of labeling of cysteine by [3H]N-ethylmaleimide. These experiments failed to detect a conformational difference between the CAP-class D and CAP-cAMP complexes. Filter binding and nuclease protection experiments indicate that the class D analogs do not efficiently support the binding of CAP to DNA. From these results, we suggest that there exists a hitherto undetected event dependent on cAMP, and required for CAP to bind to DNA. We suggest that this event involves a change that takes place in proximity to the N6 atom of cAMP. Three possible interpretations are discussed.
Ebright, RH, Cossart P, Gicquel-Sanzey B, Beckwith J.  1984.  Molecular basis of DNA sequence recognition by the catabolite gene activator protein: detailed inferences from three mutations that alter DNA sequence specificity.. Proceedings of the National Academy of Sciences of the United States of America. 81(23):7274-8. Abstract
Previously, we reported that substitution of Glu-181 of the catabolite gene activator protein (CAP) by lysine, leucine, or valine results in a protein that has specificity for A X T base pairs at positions 7 and 16 of the DNA recognition site, rather than G X C base pairs as is the case with the wild-type CAP. In this paper, we deduce from these genetic data both (i) the specific chemical interactions by which amino acid side chains at position 181 interact with base pairs 7 and 16 and (ii) the precise alignment between the structures of the CAP and DNA in the intermolecular CAP-DNA complex. Our analysis supports the idea that the two symmetry-related F alpha-helices of the CAP dimer interact with successive major grooves of right-handed B-type DNA [Pabo, C. & Lewis, M. (1982) Nature (London) 298, 443-447; and Steitz, T., Weber, I. & Matthew, J. (1983) Cold Spring Harbor Symp. Quant. Biol. 47, 419-426].
Ebright, RH, Ebright YW, Pendergrast PS, Gunasekera A.  1990.  Conversion of a helix-turn-helix motif sequence-specific DNA binding protein into a site-specific DNA cleavage agent.. Proceedings of the National Academy of Sciences of the United States of America. 87(8):2882-6. Abstract
Escherichia coli catabolite gene activator protein (CAP) is a helix-turn-helix motif sequence-specific DNA binding protein [de Crombrugghe, B., Busby, S. & Buc, H. (1984) Science 224, 831-838; and Pabo, C. & Sauer, R. (1984) Annu. Rev. Biochem. 53, 293-321]. In this work, CAP has been converted into a site-specific DNA cleavage agent by incorporation of the chelator 1,10-phenanthroline at amino acid 10 of the helix-turn-helix motif. [(N-Acetyl-5-amino-1,10-phenanthroline)-Cys178]CAP binds to a 22-base-pair DNA recognition site with Kobs = 1 x 10(8) M-1. In the presence of Cu(II) and reducing agent, [(N-acetyl-5-amino-1,10-phenanthroline)-Cys178]CAP cleaves DNA at four adjacent nucleotides on each DNA strand within the DNA recognition site. The DNA cleavage reaction has been demonstrated using 40-base-pair and 7164-base-pair DNA substrates. The DNA cleavage reaction is not inhibited by dam methylation of the DNA substrate. Such semisynthetic site-specific DNA cleavage agents have potential applications in chromosome mapping, cloning, and sequencing.
Ebright, RH, Kolb A, Buc H, Kunkel TA, Krakow JS, Beckwith J.  1987.  Role of glutamic acid-181 in DNA-sequence recognition by the catabolite gene activator protein (CAP) of Escherichia coli: altered DNA-sequence-recognition properties of [Val181]CAP and [Leu181]CAP.. Proceedings of the National Academy of Sciences of the United States of America. 84(17):6083-7. Abstract
It has been proposed that Glu-181 of the catabolite gene activator protein (CAP) makes direct contact with certain base pairs of the specific DNA site. We have purified wild-type CAP and two substituted CAP variants, [Val181]CAP and [Leu181]CAP, and have assessed the DNA-sequence-recognition properties in vitro with respect to positions 5, 6, 7, 8, and 16 of the DNA site. The data indicate that [Val181]CAP and [Leu181]CAP fail to discriminate between the consensus DNA base pair and the three non-consensus-DNA base pairs at 2-fold-related positions 7 and 16 of the DNA site. In contrast, [Val181]CAP and [Leu181]CAP retain the ability to discriminate between different base pairs at positions 5 and 8 of the DNA site. We conclude that Glu-181 of CAP makes a direct contact with 2-fold-related positions 7 and 16 of the DNA site, as proposed previously based on in vivo results. We propose that upon replacement of Glu-181 by valine or leucine, this contact is eliminated and is replaced by no other functional contact. We estimate that the contact by Glu-181 with each position contributes -0.7 kcal/mol to the total CAP-DNA binding free energy.
Ebright, RH.  1985.  Use of "loss-of-contact" substitutions to identify residues involved in an amino acid-base pair contact: effect of substitution of Gln18 of lac repressor by Gly, Ser, and Leu.. Journal of biomolecular structure & dynamics. 3(2):281-97. Abstract
A procedure to identify which base pair of lac operator (lacO) a suspected contacting amino acid of Lac repressor (LacR) interacts with is presented. The procedure is to eliminate the ability of the amino acid under study to contact DNA, and then to determine at which base pair--if any--specificity is eliminated. To implement this procedure, four sets of Escherichia coli K-12 strains have been constructed. These strains permit: (i) the substitution of a selected amino acid of LacR by, respectively, Gly, Ser, Leu, or Gln, and (ii) the analysis of the specificity of the resulting substituted LacR with respect to base pairs 5, 6, 7, 8, 9, and 10 of lacO. This procedure has been applied to Gln18 of LacR. The preliminary data indicate that LacR (Gln18----Gly) is unable to distinguish between the O+ base pair G:C and the Oc base pair T:A at position 7 of lacO (KDOc/KDO+ = 0.93). In contrast, LacR(Gln18----Gly) discriminates O+ from Oc by a factor of 13 to 23 at each other position. The same qualitative pattern of results was obtained with LacR(Gln18----Ser) and LacR (Gln18----Leu). Therefore, I propose that Gln18 contacts base pair 7 of lacO. This proposal is consistent with the contact predicted in Ebright, R. in Protein Structure, Folding, and Design. D. Oxender ed., Alan R. Liss, New York (1985), in press.
Ebright, RH, Beckwith J.  1985.  The catabolite gene activator protein (CAP) is not required for indole-3-acetic acid to activate transcription of the araBAD operon of Escherichia coli K-12.. Molecular & general genetics : MGG. 201(1):51-5. Abstract
Kline et al. (1980) have reported that indole-3-acetic acid (IAA) and four other indole derivatives are able to substitute for cAMP in activating expression of the ara regulon of E. coli. We have examined this phenomenon in detail, utilizing fusions between the structural gene for beta-galactosidase and the promoters for the araBAD, araE, and araFG operons. We confirm that IAA potently stimulates transcription from the araBAD promoter. The effect is highly specific to araBAD, as IAA has no, or only slight, effects on the araE and araFG operons. However, contrary to the results of Kline et al., we find that the action of IAA does not require CAP. Thus, IAA fully stimulates the transcription of araBAD in a strain which bears a complete deletion of the crp gene.
Ebright, RH, Connell ND.  2002.  Bioweapon agents: more access means more risk.. Nature. 415(6870):364.