Cooperative binding of fluorescein-labeled clupeine by DNA

Albumin-protamine-oligonucleotide nanoparticles as a new antisense delivery system. Part 1: physicochemical characterization

In this paper, a ternary system of albumin-protamine-oligonucleotide nanoparticles (AlPrO-NP) recently developed by Vogel et al. [V. Vogel, D. Lochmann, J. Weyermann, G. Mayer, C. Tziatzios, J.A. van den Broek, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which could serve as a potential drug delivery system for antisense oligonucleotides. Former studies of binary protamine-oligonucleotide nanoparticles showed two main disadvantages: (i) aggregation of the particles within a few minutes in the presence of salt; (ii) low intracellular dissociation between protamine and oligonucleotide, especially phosphorothioates. To overcome these problems, human serum albumin (HSA) as a non-toxic, biodegradable macromolecule was introduced as protective colloid. The assembly process of AlPrO-NP was investigated by small angle X-ray scattering (SAXS), fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS) measurements and scanning electron microscopy (SEM). 'Initial complexes' of HSA and protamine sulphate with a mean hydrodynamic diameter (dh) of about 10-14 nm were found. After adding oligonucleotides (unmodified, phosphorothioate DNA and small interfering RNA), nanoparticles (NPs) were assembled in water and in isotonic media with a dh in a range of 230-320 nm for most preparations. The chemical composition of the particles was investigated by high performance liquid chromatography and fluorescence spectrometry. The whole amount of oligonucleotides (30 microg) was entrapped into the particles at a 1:2 mass ratio (oligonucleotide/protamine). Approximately 7-10% (w/w) of the HSA was bound to the particles. The surface charge of the particles ranged from about +12 to -60 mV depending on the protamine concentration and the ionic conditions. The size and the molecular weight of the components, initial complexes and two model NP preparations were calculated from FCS data. These data verified the PCS, SEM and SAXS measurements.

Physicochemical characterization of protamine-phosphorothioate nanoparticles

Protamine-oligonucleotide nanoparticles represent effective colloidal drug carriers for antisense phosphorothioate oligonucleotides (PTO). This study describes improvements in particle preparation and the physicochemical properties of the complexes prepared. The influence of component concentrations, length of the PTO chain and the PTO/protamine weight ratio on particle formation and size, shape and surface charge of the particles were studied in detail. Nanoparticles with diameters of 90-200nm were obtained, using protamine free base (PFB) and phosphorothioate in water. The chemical composition of the nanoparticles was analysed. More than 90% of the PTO could be assembled in the particle matrix using a > or = 1:2 ratio (w/w) of PTO and PFB. About 53-68% of the PFB was incorporated in the particle matrix. The complexes had a zetapotential of -19 up to +32 mV, depending on the PTO/PFB ratio. The kinetics of the assembly of this binary system were observed by dynamic light scattering (DLS) measurements and by sedimentation velocity analysis in the analytical ultracentrifuge (AUC). In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to verify the results of DLS and the ultracentrifuge measurements. According to sedimentation velocity analysis, the particles were only moderately stable in water and unstable in salt solutions. However, the colloidal solution in water could be stabilized by polyethylenglycol 20000 (PEG), which also led to an increase of stability in cell medium.

Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties, and intracellular distribution

Oligodesoxynucleotides (ODNs) or the corresponding phosphorothioates (PTOs) spontaneously form spherical nanoparticles ("proticles") with protamine in aqueous solutions. The proticles can cross cellular membranes and release the ODNs within the cells. Thus, they represent a potential drug delivery system. The major disadvantages of this system are a lack of stability in salt solutions and its inability to also release PTOs. The present study shows, using PTOs and protamine free base, that these shortcomings can be eliminated by the addition of human serum albumin (HSA) as a third component to the starting mixture. The "ternary" proticles thus obtained contain maximally a few percent of the HSA that was originally present. Nevertheless, they differ from the previously studied "binary" proticles: (1) They are stable in salt solutions for at least several hours. (2) They show a high cellular uptake into murine fibroblasts, and they readily release the PTOs after uptake. The ternary proticles therefore represent a considerable improvement over binary proticles for use as drug delivery systems.

Intracellular tracking of protamine/antisense oligonucleotide nanoparticles and their inhibitory effect on HIV-1 transactivation

Membrane transport of antisense oligonucleotides (ODN) is an inefficient process which requires special carriers for their intracellular delivery. We have developed a delivery system for AS-ODN and their phosphorothioate analogues (AS-PTO) directed against human immunodeficiency virus type 1 (HIV-1) tat mRNA for efficient transfection of HIV-1 target cells. Protamine was used to complex AS-ODN and AS-PTO to form nanoparticles with diameters of about 180 nm and surface charges in the range of -18 to +30 mV. Cellular uptake of these nanoparticles was significantly enhanced compared to naked oligonucleotides. A double labeling technique with fluorescently tagged protamine and AS-ODN was used to follow the intracellular fate of the nanoparticles. Protamine/AS-ODN nanoparticles showed release of the antisense compound leading to specific inhibition of tat mediated HIV-1 transactivation. In contrast, protamine/AS-PTO complexes were stable over 72 h, and failed to release AS-PTO. These results demonstrate that protamine/AS-ODN nanoparticles are useful for future therapeutical application to inhibit viral gene expression.

New protamine quantification method in microtiter plates using o-phthaldialdehyde/N-acetyl-l-cysteine reagent

Protamine is a well-known excipient in pharmaceutics. It represents a peptide consisting of exclusive aliphatic amino acids, hence it cannot be quantified by UV-spectroscopy (lambdamax 280 nm). A new and sensitive quantification method based on the derivatisation of protamine with ortho-phthaldialdehyde (OPA) in the presents of 2-mercaptoethanol (ME) or N-acetyl-L-cysteine (NAC) in basic aqueous solution using 96-well microtiter plates are introduced in this report. The resulting isoindol derivatives reveal a fluorescence excitation (maximum lambdaex 345 nm) and emission (maximum lambdaem 450 nm) spectra. Derivatives of OPA/NAC reagent were found to be useful for protamine quantification in pharmaceutical nanoparticle preparation containing DNA. A sufficient stability of the isoindol derivatives was shown. It was possible to determine protamine free base, protamine sulphate and protamine chloride with limits of detection less than 1.1 microg/ml.

Are there molecules of nucleoprotamine?

A short critical review of the data related to protamine and nucleoprotamine (DNP) structure is given. A new model is proposed for DNP structure in which protamine molecules are located in channels between the DNA molecules. DNA molecules are arranged hexagonally in the x-y plane, whereas their relative positions with respect to the z-axis are shifted by 0, 1/3, and 2/3 of the pitch of the double helix. As a result, large cavities are formed in three out of six channels surrounding each DNA molecule where the large grooves are juxtaposed. Protamine molecules are also proposed to have some secondary/tertiary structure prior to complex formation. Inside the channels, a protamine molecule modifies its shape to fill the large grooves of all of the three surrounding DNA molecules simultaneously, and might possibly be in touch with other protamine molecules in neighbouring positions as well. This disposition allows the protamine molecules to be located between DNA molecules without a significant increase in the lattice parameters.

Rearrangements of chromatin structure during spermatogenesis of squid

A stepwise replacement of somatic histones on sperm-specific proteins (we have termed them illexines I1 and I2) is found to occur during spermatogenesis of squid Illex argentinus [Kadura, S.N. and Khrapunov, S.N. (1988) Eur. J. Biochem. 175, 603-607]. The chromatin from nuclei of squid immature testes has a nucleosomal DNA repeat which corresponds to the nucleosomal repeat of calf thymus chromatin (195 +/- 5 bp). As spermatozoa become mature and illexine I2 accumulates in the chromatin, the nucleosomal structure of the latter disappears and chromatin compacting takes place. The chromatin DNA from squid spermatozoa is highly resistant to micrococcal nuclease action. Spectrophotometry and spectrofluorimetry were to establish that neither illexine I1 nor illexine I2 forms a globular structure in solution under any conditions studied. Illexine I2 (approx. 7 kDa) shows a high affinity to DNA and remains bound to it under conditions when complexes of illexine I1 (approx. 9 kDa) and salmine (approx. 4.5 kDa) with DNA completely dissociate. This fact, allowing for a similar content (about 75%) of arginine in illexine I2 and salmine, suggests high clustering of arginine residues in the composition of illexine I2. It is suggested that the initial stage of histone substitution with illexine I1, which has a more moderate affinity to DNA than illexine I2, prepares chromatin for the formation of a highly packed structure by illexine I2 during squid spermatogenesis.

Fluorescence studies on clupein protamines: evidence for globular conformation

Conjugates of fluorescein isothiocyanate with clupein YI, YII and Z, the protamines from Clupea palasii, were prepared and their fluorescence utilized to determine the rotational relaxation times of the proteins. All conjugates exhibited single component lifetimes near 4.05 ns. Linear isothermal Perrin plots were obtained for all conjugates; these data indicated rotational relaxation times of 3.33 ns for clupein YI and YII and 3.19 ns for clupein Z. These results and the results from our previous studies lead us to postulate globular conformations for the three proteins with hydrated molecular diameters of 22 A. Based on these findings a three dimensional model for Clupein YII is proposed.

New anthracenedione derivatives: interaction with DNA and biological effects

Two anthracenedione derivatives [1 - (omega - diethylaminopropylamido) - 4 - hydroxy - 9,10 - anthracenedione hydrochloride (I) and 1 - (omega - diethylaminopropylamido) - 2 - methoxy - 4 - hydroxy - 9, 10 - anthracenedione hydrochloride (II)], having an electron-rich planar chromophore and an amino-substituted side chain, have been synthesized. Their binding ability to DNA was investigated by means of spectroscopic, equilibrium dialysis and fluorescence measurements. Their inhibition efficiency on nucleic acid synthesis was also evaluated both in mouse and human cells. Our results indicate that, in comparison with adriamycin, compound I shows a slightly weaker complexation ability to DNA, while compound II interacts with DNA at a substantially lower level. These data match quite well with the biological response on the inhibition of DNA and RNA synthesis exhibited by the above mentioned compounds; in fact compound I is slightly less efficient than adriamycin and about ten times more efficient than compound II. The close relationship between the results of physicochemical and biological studies is discussed.

Isolation and characterization of nuclear basic protein (protamine) from boar spermatozoa

1. Sperm nuclei were isolated and purified from boar semen by a procedure involving differential solubilization of sperm tail and acellular materials by brief exposure to reducing reagent in the presence of cationic detergent, and sedimentation through 60% sucrose. The weight ratio of DNA:RNA: total protein: protamine in this preparation was 1.00: 0.02: 1.05: 0.75, and the molar ratio of phosphorus to arginine was 1.12. 2. Boar protamine was extracted with cold acid from ethanol precipitate of reduced and carboxymethylated nuclei in 6 M guanidine hydrochloride and purified by ion-exchange chromatography on CM-cellulose. The molecular weight of the protamine was estimated to be 6600 by the gel filtration method. The protamine consisted of a single amino terminus alanine and either half-cystine or arginine as carboxy terminus, and was composed of Thr, Ser3, Pro2, Ala2, Val2, Ile, His, Half-cystine9-10 and Arg26 . 3. Chymotryptic digestion gave rise to a single amino-terminal peptide, Ala-Arg-Tyr, and two carboxy-terminal peptides, Thr-Val-Ile-Arg-Cys-Arg2-Cys and Thr-Val-Ile-Arg-Cys-Arg2, which confirmed the heterogeneity of the protamine at the carboxy-terminal end.

The binding of protamines to DNA; role of protamine phosphorylation

The thermodynamics of protamine-DNA interation was investigated with clupeine Z from herring labeled at its amino terminus with fluorescein. The ionic strength dependence, the influence of protamine phosphorylation, of the native DNA conformation, using native and heat-denatured DNA, and of the protamine primary structure, using two oligoarginine peptides of similar length as the clupeine, was thoroughly studied. The unusually high cooperativity of interaction found is strictly correlated to the native DNA conformation and the protamine primary structure. Cooperativity is explained by cross-linking of DNA segments resulting in an increase of the negative charge density. The importance of protamine phosphorylation lies in the fact that thermodynamically governed interaction with DNA and favorable cross-linking of DNA are shifted to physiologically reasonable ionic strengths.

Phosphorylated protamines. I. Binding stoichiometry and thermal stability of complexes in DNA

To decipher on a molecular level the role of protamine phosphorylation in spermiogenesis, clupeine Z species containing one, two or three serine phosphates were prepared utilizing a recently developed chemical procedure. The melting of complexes with calf thymus DNA showed that thermal stability decreases with increasing degree of phosphorylation. The stoichiometry of the nucleoprotamine complexes was investigated analyzing the melting curves and using the fluorescamine assay recently described. Phosphorylation significantly reduces binding stoichiometry defined as DNA-nucleotides covered by a protamine molecule. Thus, phosphorylated protamines are more densely packed along DNA; the implications on processes occurring in spermiogenesis as i. e. histone replacement, are discussed. A general discussion on the variability in protein-DNA stoichiometry values obtained by different procedures is included.

Phosphorylated protamines. II. Circular dichroism of complexes with DNA, dependency on ionic strength

The influence of protamine phosphorylation upon the conformation of nucleoprotamine complexes was studied at different ionic strengths using circular dichroism. The sharp onset of CD spectral changes upon decreasing the NaC1 concentrationwas correlated with the beginning of complex formation and can be used to determine apparent binding affinities in terms of a critical ionic strength. It is show that phosphorylation strongly reduces the binding strength of protamines towards DNA. Directly mixed and reconstituted complexes reveal differences in their CD spectra, which decrease with increasing ionic strength. Spectra of complexes between threefold phosphorylated clupeine Z and DNA obtained by reconstitution or direct mixing at higher ionic strength resemble the phi-type spectra of DNA and are unique for the phosphorylated species. The implications of protamine phosphorylation for chromatin or DNA condensation havebeen discussed.

On the competition between protamines and histones: studies directed towards the understanding of spermiogenesis

Specific contacts between the crossinteracting histones effectively prevent their protamine-mediated displacement from nucleoproteins revealing a complex competition pattern not expected from their relative affinities to DNA. Histone H1 is the only species freed under a variety of conditions if native chromatin is used; the results found with chromatins obtained by conventional methods reflect the extent to which histone redistribution has occurred. It is concluded that the events occurring during spermiogenesis must be apt to disrupt histone interactions found in the nucleosomes. The possible role of a protamine phosphorylation/dephosphorylation mechanism is discussed on the basis of comparative experiments with protamines phosphorylated to different extents.