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Emerging evidence suggests that small vessel disease (SVD) is a risk factor for clinical dementia and may contribute to AD neuropathological changes. Watershed brain regions are located at the most distal areas between arterial territories, making them vulnerable to SVD-related changes. We examined the association of pathologic markers of SVD, specifically arteriolosclerosis in watershed brain regions, with AD pathologic changes. Participants (N = 982; mean age-at-death = 90; 69% women) were enrolled as part of one of two cohort studies of aging and dementia. At autopsy, neuropathological evaluation included semi-quantitative grading of arteriolosclerosis pathology from 2 cortical watershed regions: the anterior watershed (AWS) and posterior watershed (PWS), densities for cortical β-amyloid and tau-tangle pathology, and other common age-related pathologies. Linear regression models examined the association of watershed arteriolosclerosis pathology with β-amyloid and tau-tangle burden. In follow-up analyses, available ex-vivo MRI and proteomics data in a subset of decedents were leveraged to examine the association of whole brain measure of WMH, as a presumed MRI marker of SVD, with β-amyloid and tau-tangle burden, as well as to examine the association of watershed arteriolosclerosis with proteomic tau. Watershed arteriolosclerosis was common, with 45% of older persons having moderate-to-severe arteriolosclerosis pathology in the AWS region, and 35% in the PWS. In fully adjusted models that controlled for demographics and common age-related pathologies, an increase in severity of PWS arteriolosclerosis was associated with a higher burden of tau-tangle burden, specifically neocortical tau burden, but not with β-amyloid. AWS arteriolosclerosis was not associated with β-amyloid or tau pathology. Ex-vivo WMH was associated with greater tau-tangle pathology burden but not β-amyloid. Furthermore, PWS arteriolosclerosis was associated with higher abundance of tau phosphopeptides, that promote formation of tau aggregates. These data provide compelling evidence that SVD, specifically posterior watershed arteriolosclerosis pathology, is linked with tau pathological changes in the aging brain. [ABSTRACT FROM AUTHOR]

Kinetic parameters of cleavage of CpA and UpA sites in an oligoribonucleotide under the action of artificial ribonuclease ABL3C1 were measured. The compounds were built of RNA-binding domain B, catalytic fragment C, linker L3 comprising 3 methylene groups, and aliphatic fragment A. The rate of cleavage of phosphodiester bonds in the CpA site within decaribonucleotide UUCAUGUAAA was shown to be 3.4 ± 0.2 times higher than in UpA. The rate of cleavage of phosphodiester bonds was found to depend on substrate length: a thousandfold increase in cleavage rate constant was observed for the CpA site in decaribonucleotide as compared with diribonucleoside monophosphate CpA. A slight decrease in the cleavage rates was observed for the reactions proceeding in different buffers at pH 7.0: imidazole > HEPES > phosphate > cacodylate. At the same time, the ratio of cleavage rates for CpA and UpA sites remained constant. [ABSTRACT FROM AUTHOR]

With the object of elucidating the factors that affect the rate and efficiency of oligonucleotide hybridization with complementary regions in natural RNA, the interaction of tRNAPhe and in vitro transcript of this tRNA with synthetic oligonucleotides matching the 32—61 region comprising the variable loop and anticodon and TΨC stems of the molecule was studied in detail. Gel retardation was used to assay thermodynamic and kinetic parameters of tRNA interaction with oligonucleotides. Oligonucleotide hybridization rates do not depend on the oligonucleotide length and are determined by the stability of RNA structure within the binding site. The rate constant for hybridization correlates with the number of base pairs in the RNA opened during binding with the oligonucleotide. Factors stabilizing the tRNA secondary structure (the presence of Mg2+ ions, low temperature, hypermodified bases) decrease significantly both the rate and efficiency of hybridization. Analysis of the tRNAPhe structure in the presence of an oligonucleotide shows that binding of oligonucleotides with the 45—61 region of tRNAPhe results only in unfolding of the TΨC hairpin and does not disturb the secondary structure of the rest of the molecule. [ABSTRACT FROM AUTHOR]

Interaction of yeast phenylalanine tRNA with oligonucleotides complementary to its 3′-terminal nucleotide sequence was thoroughly studied. Using the gel retardation technique, thermodynamic and kinetic parameters of the tRNA complexation in physiological conditions were determined. Analysis of dependences of the complex formation on the oligonucleotide concentration and incubation time showed that this process proceeds in two stages. At the first stage, a metastable complex of the oligonucleotide with the open, single-stranded sequence ACCA at the 3′ end of tRNA rapidly forms. The second stage involves a slow intramolecular rearrangement of the resulting metastable complex into a full-sized heteroduplex accompanied by the tRNAPhe unfolding. The data gained suggest that the RNA unfolding stage is limiting in the interaction of oligonucleotides with natural RNAs. Principles of selection of optimal hybridization probes and antisense oligonucleotides are discussed. [ABSTRACT FROM AUTHOR]