From Big Medical Encyclopedia

SUPPRESSION (Latin suppressio pressure, suppression) — suppression of the sign which resulted from a mutation i.e. recovery at a mutant of a former phenotype owing to interaction of mutations, as a result to-rogo one mutation partially or completely suppresses phenotypical manifestation another. By page it was found in 1920 an amer. geneticist A. H. Sturtevant.

At intragenic S. mutations among themselves interact (see. Mutation ), localized in one gene (see). Such interaction can happen during the reading of a genetic code (see) when direct mutation — an insert (or loss) — leads couples of nucleotides in DNA to shift of reading and distortion of meaning of genetic information, and suppressor mutation — loss (or an insert) couples of nucleotides — leads to the return shift of reading and by that to recovery of sense of genetic information outside the site concluded between two mutations. This type of intragenic suppression at a bacteriophage of T4 in 1961 used F. Shout, etc. for establishment of the general structure of a genetic code. Intragenic S. can occur also at interaction of two amino-acid replacements in one protein which are a consequence of direct and suppressor mutations. At the same time the second change compensates action of the first defect that leads to formation of functionally active spatial structure of protein, synthesis to-rogo is coded by the mutating gene.

At intergene, or gene, S. interact mutations of different genes. The following mechanisms intergene are known to Page. As a result of suppressor mutation the alternative way of formation of that metabolite, synthesis appears to-rogo it was blocked by direct mutation. Suppressor mutation can change the intracellular environment, to a cut shows hypersensitivity mutant enzyme. Perhaps also leading to normalization of a phenotype, i.e. to recovery of the lost enzymatic activity, direct interaction of two proteins: the protein changed owing to direct mutation, and the protein changed owing to suppressor mutation.

Information (or transmitting) S., edges consists in mutational change of one of the components providing process broadcastings (see), leads to change of sense of a mutant codon. At the same time distinguish noncence supression when there is a comprehension of senseless codons, and missens-suppression when there is a change of sense of the mutant meaning codons. As shown for bacteria and yeast, transmitting noncence supression is possible at the expense of various TRNK, to-rye owing to change of an anti-codon become capable to read out a nonsense codons — UAG, UAA, UGA (At — uracil, And — adenine — guanine). Missens-supressiya, in detail investigated at bacteria, occurs owing to change of an anti-codon only of one class TRNK — glycine (glycyl-) TRNK, to-rye become capable to consider codons for nek-ry other amino acids as a codon for glycine.

Due to change of TRNK also transmitting S. of the shifts of reading arising owing to inserts or losses of couple of nucleotides in any gene is possible. In this case suppressor activity of TRNK is shown owing to an insert or loss of a nucleotide in its anti-codon that leads to reading of four or two bases (instead of three, as usual). All three types of mutational changes: the nonsense codons, missens-codons and shifts of reading can be soup-ressirovany owing to mutational change ribosomes (see).

Genotypic S.'s research is used for clarification of interaction of different stages of cellular metabolism, and also interactions between components of the device of proteinaceous synthesis — aminoacyl-TRNK-sintetaz, TRNK and ribosomes.

Along with genotypic consider also phenotypical Page. In this case normalization of a phenotype at mutants happens without additional mutational changes, and entirely due to the modifications arising under the influence of the environment. Phenotypical S.'s research — one of perspective approaches to clarification of mechanisms modification variability (see).

Bibliography: Gorini L. Antibiotics and a genetic code, in book: Molecules and cells, the lane with English, under the editorship of G. M. Frank, century 2, page 22, M., 1967; Hartman P. E. a. R about t h J. N of Mechanisms of suppression, Advanc. in Genet., v. 17, p. 1, 1973, bib-liogr.; Hill G. W. Informational suppression of missense mutations, Cell, v. 6, p.419, 1975, bibliogr.; Rieger R., M i with h a-e 1 i s A. Green M. M. Glossary of genetics and cytogenetics, classical and molecular, N. Y., 1976.

To S. G. Inga-Vechtomov.