Hybridase cleavage of RNA. I. Oligonucleotide probes for regiospecific RNA cleavage]

New oligonucleotide probes for regiospecific cleavage of RNA molecules by hybridase (RNase H) are suggested. RNase H from E. coli is shown to site-specifically split eight phosphodiester bonds in RNA in the heteroduplex, formed by 5S rRNA and d(ACCACCGCGCT). The partial substitution of deoxycytidines in position 5, 6, 8, 10 of the probe by 2'-O-methylcytidines leads to unique (regiospecific) RNA cleavage between U25 and C26.     

Site-specific enzymatic cleavage of TMV RNA directed by deoxyribo- and chimeric (deoxyribo-ribo)oligonucleotides

The TMV RNA molecule can be cleaved at a single site by RNase H directed by chimeric oligo(deoxyribo-ribo)nucleotide with an internucleotide pyrophosphate bond.     

Hairpin-shaped DNA duplexes with disulfide bonds in sugar-phosphate backbone as potential DNA reagents for crosslinking with proteins

Convenient approaches were described to incorporate -OP(=O)O(-)-SS-O(-)(O=)PO- bridges in hairpin-shaped DNA duplexes instead of regular phosphodiester linkages: (i) H2O2- or 2,2'-dipyridyldisulfide-mediated coupling of 3'- and 5'-thiophosphorylated oligonucleotides on complementary template and (ii) more selective template-guided autoligation of a preactivated oligonucleotide derivative with an oligomer carrying a terminal thiophosphoryl group. Dithiothreitol was found to cleave completely modified internucleotide linkage releasing starting oligonucleotides. The presence of complementary template as an intrinsic element of the molecule protects the hairpin DNA analog from spontaneous exchange of disulfide-linked oligomer fragments and makes it a good candidate for auto-crosslinking with cysteine-containing proteins.     

Covalent binding of Cys142 from SsoII methyltransferase with DNA duplexes, containing a phosphoryldisulfide internucleotide group

DNA duplexes containing a single phosphoryldisulfide link in place of the natural internucleotide phosphodiester bond were employed in affinity modification of Cys142 in cytosine-C5 DNA methyltransferase SsoII (M.SsoII). The possibility of duplex-M.SsoII conjugation as a result of disulfide exchange was demonstrated. The crosslinking efficiency proved to depend on the DNA primary structure, modification position, and the presence of S-adenosyl-L-homocysteine, a nonreactive analog of the methylation cofactor. The SH group of M.SsoII Cys142 was assumed to be close to the DNA sugar-phosphate backbone in the DNA-enzyme complex.     

Synthesis and properties of oligodeoxyribonucleotids with mono- and diphosphoryldisulfide internucleotide groupings

The synthesis of oligodeoxyribonucleotides bearing mono- and diphosphoryldisulfide internucleotide links was optimized. Oligonucleotide 3'-thiophosphorothioates were modified using the thiophosphoryl-disulfide exchange with preactivated 5'-deoxy-5'-mercaptooligonucleotides or 5'-phosphorothioate derivatives both with and without a complementary template. The lack of template was shown to differently affect the product ratio (homo- and heterodimers) in the reactions of mono- and diphosphoryldisulfide-containing oligonucleotides. A replacement of one natural phosphodiester bond in 15-16-mer duplexes by a mono- or diphosphoryldisulfide group causes a slight thermal destabilization of the corresponding duplex. The disulfide recombination of the resulting compounds was studied.     

The Synthesis and Properties of Oligodeoxyribonucleotides with Single Mono- and Diphosphoryldithio Internucleotide Links

The synthesis of oligodeoxyribonucleotides bearing mono- and diphosphoryldisulfide internucleotide links was optimized. Oligonucleotide 3"-phosphorothioates were modified using the thiophosphoryl–disulfide exchange with preactivated 5"-deoxy-5"-mercaptooligonucleotides or 5"-phosphorothioate derivatives both with and without a complementary template. The lack of template was shown to differently affect the product ratio (homo- and heterodimers) in the reactions of mono- and diphosphoryldisulfide-containing oligonucleotides. A replacement of one natural phosphodiester bond in 15–16-mer duplexes by a mono- or diphosphoryldisulfide group causes a slight thermal destabilization of the corresponding duplex. The disulfide recombination of the resulting compounds was studied.     

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.