Medicine for RNA

The pathogenic RNA defect was blocked by a low molecular weight compound

Oleg Lischuk, N+1

American scientists have found a low-molecular compound that is able to block one of the types of RNA defect and eliminate the manifestations of the disease caused by this defect in human cell culture. The development report is published in the journal Nature Communications (Yang et al., Design of a bioactive small molecule that targets r(AUUCU) repeats in spinocerebellar ataxia 10).

Researchers at the Scripps Research Institute and the University of Texas conducted a search for molecules capable of blocking RNA sites containing multiple repeats.

2AU-2. Here and below are drawings from an article in Nature Communications

Such repetitive sequences lead to the synthesis of defective proteins and, according to Matthew Disney, the head of the work, underlie the development of more than 30 diseases that are currently incurable (see the press release of Scripps Florida scientists create compound that erases disease-causing RNA defect).

Scientists have developed a two-dimensional combinatorial screening technique that allows to determine the interaction of specific pairs of RNA nucleotides with low-molecular compounds having affinity for nitrogenous bases. These compounds – derivatives of benzimidazole, benzamidine and aniline – were taken from the libraries of the Scripps Institution and the National Cancer Institute. For the convenience of the study, only fluorescent molecules were selected, there were 104 of them.

These compounds were incubated with different types of RNA to reveal their affinity for nitrogenous bases and selectivity. Based on the chemical structure of the selected substances, scientists have constructed a Venn diagram (a schematic representation of all possible intersections of several sets), which allows to identify their features that ensure selectivity for given nucleotide pairs: adenine-uracil (AU) and guanine-cytosine (HC). The most suitable candidate molecules were tested for affinity to the specified types of RNA.

Venn diagram and benzamidine derivatives with high affinity for AU

It turned out that two benzamidine derivatives selectively bind to AU. These compounds were used to bind pentanucleotide repeats of AUUTSU, which cause mitochondrial dysfunction and activation of apoptosis (natural cell death), leading to the development of a serious disease – spinocerebellar ataxia type 10 (SCA-10, manifested by progressive coordination disorders and paralysis of the hands). According to the results of the experiment, the scientists selected one of the substances (it was given the designation AU by the nucleotide target) to create polyvalent modules that bind the specified repeats.

From two AU azide molecules connected by peptide chains of different lengths, the researchers created 2AU-n dimers and tested them for their ability to block the sequence of pentapeptide repeats of AUUTSU. It turned out that a dimer containing two peptide bonds (2AU-2) is best suited for these purposes.

Structure of 2AU-n dimers

This compound was tested on fibroblast culture of patients with SCA-10. In 48 hours, 2AU-2 in a 50-nanomolar concentration reduced the activity of the enzyme of apoptosis of caspase-3 to normal values and reduced the proportion of affected mitochondria from 70-80 to 10-15 percent. The experiment with healthy cells revealed no signs of toxicity of the compound.

Thus, 2AU-2 became the first low molecular weight substance that selectively binds RNA repeats and prevents their undesirable biological effects, which makes it a candidate drug for the treatment of CCA-10. The developed approach can be used in creating compounds that bind other (potentially any) repeated sequences leading to various diseases, such as Huntington's disease, myotonic dystrophy types 1 and 2, and others.

Portal "Eternal youth" http://vechnayamolodost.ru  02.06.2016