Changes in the thermal denaturation profiles of DNA from different developmental stages of the newtTriturus vulgaris

Summary The melting profiles of DNA samples from the early gastrula and early neurula ofTriturus vulgaris are essentially the same, whereas DNA from mid to late gastrula possesses higher T_m values and shows a deviation from the regular sigmoidal shape at temperatures above T_m. The plot on normal probability paper indicates a second DNA fraction which melts at higher temperatures and, consequently, it has a higher GC-content than the bulk DNA. These facts confirm our idea that differential DNA replication occurs during gastrulation.     

Specific isomerization of rhodopsin-bound 11-cis-retinal to all-trans-retinal under thermal denaturation

The natural ligand of the retinal photoreceptor rhodopsin, 11-cis-retinal, is isomerized to its all-trans configuration as a consequence of light absorption in the first step of the visual phototransduction process. Here we show, by means of difference spectroscopy and high-performance liquid chromatography analysis, that thermal denaturation of rhodopsin induces the same type of isomerization. This effect is likely due to thermally induced conformational rearrangements of amino acid residues in the retinal-binding pocket – possibly implying helical movements – and highlights the tight coupling between 11-cis-retinal and opsin. This effect could have implications in the instability and functional changes seen for certain mutations in rhodopsin associated with retinal disease, and in the stability of the different conformers induced by mutations in other G protein-coupled receptors.Received 25 March 2003; received after revision 6 August 2003; accepted 9 September 2003     

Hydrolysis of histones by horse urinary kallikreins

Summary Horse urinary kallikrein was shown to hydrolyze histones from calf thymus and chicken nuclei erythrocytes. The hydrolysis is inhibited by benzamidine and hyposulfite but not by soy-bean trypsin inhibitor; horse plasma kallikrein also produces this hydrolysis.Work supported by grants from Projeto BIOQ/FAPESP (São Paulo), FINEP (Rio) and CNPq (Rio).Fellow from CNPq, from Instituto Biológico (São Paulo).     

Inhibition of amphibian egg development by histones

Riassunto Uova di Anuri (Discoglossus pictus) sono state trattate con istoni. II trattamento con la frazione ricca in lisina (0,4-0,1 mg/ml) durante la segmentazione causa blocco alle prime divisioni. Con concentrazioni minori (0,05–0,025 mg/ml) lo sviluppo si arresta allo stadio di gastrula. La sensibilità al trattamento decresce notevolmente dopo la gastrulazione. La frazione ricca in arginina è risultata meno efficace.     

Inhibition of RNA polymerase activity by arginine-rich histones

Zusammenfassung Im Komplex mit der DNS-Matrize zeigt die lysinreiche Fraktion F1 eine doppelt so grosse Hemmung der RNS-Synthese in vitro als das argininreiche Histon F3. Demgegenüber erwies sich das argininreiche Histon F3, mit RNS-Polymerase komplexiert, wirksamer als das lysinreiche Histon F1, das heisst, dass die Inhibition mit dem argininreichen Histon F3 fünffache Steigerung und damit doppelte Wirksamkeit gegenüber F1 ergibt.     

Inhibitory effect of exogenous histones on cellular growth and DNA synthesis in Chlamydomonas reinhardtii.]

The addition of exogenous histones to synchronous culture of Chlamydomonas reinhardtii, at the beginning of the cell cycle, leads to the death of the cells. The same amount of histones added in the middle of the cycle, only blocks the cell division. The mechanism of this inhibition effect of the histones could involve a block at the level of the chloroplast DNA replication.     

Effects of histones on embryonic cells

Zusammenfassung Der Einfluss vom Kalbsthymus Histon (CTH) und seines diazotierten Derivatives (DCTH) auf Vitalität und Zelldifferenzierung verschiedener Gewebe des Hühnerembryos wurde geprüft. Die LD₅₀ für CTH wurde bei 25µg/ml der Zellsuspensionen festgestellt. Es wurden keine bedeutenden Änderungen in der Differenzierung der embryonalen Gewebe in Kulturen bei sublethalen Konzentrationen gefunden.     

The specificity of histones in nucleated erythrocytes

Riassunto Dagli eritrociti del pollo, dellaRana cateasbeiana e del pesceCaranx hippos sono stati isolati gli istoni nella ipotesi che gli eritrociti forniti di nucleo contengano una frazione di istone funzionante come repressore permanente della sintesi degli acidi nucleici. Detti istoni sono stati frazionati ed analizzati nella loro composizione in amino-acidi. In tutte e tre le speci su menzionate è stata trovata una frazione relativamente ricca in lisina, arginina, alanina, e serina che è stata denominata F2c. L'assenza di detta frazione negli altri tessuti incluso il midollo osseo indica che la frazione F2c può costituire un repressore genetico permanente.

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This investigation was supported by the U.S. Public HEalth Service Grant No. CA-07746, American Cancer Society Grants E-388 and IN-43-F2, and by the Robert A. Welch Foundation Grant G-138.     

The specificity of histones in chicken erythrocytes

Zusammenfassung Isolierung, qualitative und quantitative Charakterisierung der Histone von Hühnererythrocyten wird beschrieben. Mittels Gelfiltration an Sephadex G 75 wurde eine Fraktion des Histons, charakteristisch für die Hühnererythrocytenzellkerne isoliert und analysiert. Diese Fraktion, als F2c bezeichnet, ist ein Teil des lysinreichen Histons F2, reich an Lysin, Alanin, Serin und Arginin (z.B. 21,0, 15,1, 11,9 und 10,6% respektive). Threonin konnte als N-terminale Aminosäure in dieser Fraktion festgestellt werden.     

Uptake of labelled histones by isolated perfused rat liver and by various organs of the intact mouse

Résumé Des histones marquées au H³ ont été administrées à des souris par voie intrapéritonéale. La pénétration d'histones dans le foie isolé en perfusion est rapide. Les noyaux contiennent une quantité plus ou moins proportionnelle à leur volume dans la cellule et la majorité de l'activité a pu être isolée comme histones liées à la chromatine.     

Stimulation of RNA polymerase activity by histones,polyamino acids,and polypeptide hormones

Zusammenfassung Decalysin, Polyarginin, Polylysin, Polyornithin, Kalbsthymushistone und Polypeptidhormone stimulieren in niedriger Konzentration die DNA-abhängige RNS-Polymerase-Aktivität vonEscherichia coli, während sie in hoher Konzentration die Enzymaktivität hemmen.     

The fractionation of arginine-rich histones from calf thymus

Zusammenfassung Die argininreiche Fraktion des Kalbsthymushistons (Fraktion 2a) wurde in zwei Komponenten zerlegt. Zusammensetzung und elektrophoretische Trennung der Komponenten (F2a_I und F2a_II), ebenso die Eigenschaften eines neuen, lipidgebundenen, serinreichen Histons wurden beschrieben.     

Measurement of the position and intensity of chromosomal denaturation bands by an automatic system]

The band density profile of a marked chromosome was obtained using a photodiode collector combined with a minicalculator, working with an ordinary photographic document. The measurement was carried out over 10 to 20 300-point lines oriented longitudinally along the chromosome. The profile obtained corresponds to the sum of the values of each of these lines. The proposed systems's originality resides in its ability to determine the position and intensity of a band over the entire thickness of the chromosome.     

Effect of dimethyl sulfate on the secondary structure of DNA

Summary Hydroxyapatite chromatography has been used to demonstrate that alkylation of DNA at neutral pH may lead to denaturation under conditions where no significant depurination occurs. Presence of salt has a preventive effect on such denaturation.Acknowledgment. The authors are grateful to University Grants Commission, India for financial assistance to A. A. W.     

Effect of histones from brain on DNA-synthesis in vitro

The results of these experiments demonstrate that histones from brain inhibit the replication of DNA in vitro. A similar effect is observed with polylysine or polyarginine. The reversion of inhibition by polyglutamic acid or acidic proteins is completed in all cases except when the DNA is previously complexed with histones, polyarginine or polylysine. This suggest that histones masking of DNA towards the polymerases involves electrostatic forces.