[The use of p53 as a tool for human cancer therapy].

The p53 tumor suppressor is a central component of a system that reinforces genetic stability of somatic cells in animals and humans. Inactivation of this gene occurs virtually in every cancer case, which eliminates results in further rapid accumulation of additional mutations leading to progression of a cancer cell toward more malignant phenotype. The mechanisms of p53 inhibition in cancer include point mutations leading to accumulation of inactive protein, deletion of the whole gene, or its portion, alteration in the genes involved in regulation of activity of p53, and defects in the genes controlled by p53. In addition, oncogenic viruses encode specialized proteins that are entitled to modify p53 functions in order to provide optimal condition for replication of viral genome. These viral proteins play central role in viral carcinogenesis, including 95% of cases of cervical carcinoma in women. The approacheas to restoration of p53 activity depend on particular type of alteration within the p53 pathway. In some cases an effective mean would be introduction of exogenous p53, particularly with the use of adenoviral vectors. There are also approaches in development that target reactivation of mutant proteins, or suppress natural inhibitors of p53. The review summarizes various schemes for therapy and prevention of cancer that are based on our knowledge of the p53 gene functions. Potential usefulness of the approaches for practical applications is discussed.

[Dominant-negative inactivation of p53: the effect of the proportion between trans-dominant inhibitor and its target]. / Dominantno-negativnaia inaktivatsiia p53: vliianie kolichestvennykh sootnoshenii transdominantnogo ingibitora i ego misheni.

Dominant-negative mutations of the p53 tumor suppressor gene and oligomerization of the mutant and wild-type p53 are considered responsible for functional inactivation of the p53 tetramer. Although dominant-negative inactivation of p53 is well reproducible in experimental systems, its contribution to processes occurring in tumor cells heterozygous at p53 is still unclear. To study the effect of dominant-negative inhibitor GSE22 on the p53 activity, cultures coexpressing GSE22 and tetracycline-suppressible p53 were derived from p53-negative cell lines. Transcriptional activity and expression of p53 proved to depend on the proportion between p53 and GSE22. The dominant-negative effect was observed only when GSE22 was in a multifold excess to p53. GSE22 was shown to be suitable for complete reversible inactivation of p53.

[Construction of chimeric tumor suppressor p53 resistant to the dominant-negative interaction with p53 mutants]. / Sozdanie khimernoi molekuly opukholevogo supressora p53, ustoichivoi k dominantno-negatvnym vzaimodeistviiam s mutantnymi formami belka p53.

A chimeric p53 cDNA was constructed so that the fragment coding for 39 residues of the chicken p53 tetramerization domain replaced the corresponding region of human p53. The chimeric cDNA substantially inhibited the colony-forming ability of transfected human and mouse cells, suggesting a suppressory potential for its product. The chimeric p53 activated promoters containing p53-responsive elements. In contrast to wild-type human p53, the chimeric p53 remained capable of transcription activation in the presence of dominant-negative mutant p53-His175. This makes the chimeric p53 a convenient model for elaborating gene therapy protocols for tumors with dominant-negative p53 forms. The chimeric p53 may be used to study the role of transdominance of p53 mutants in carcinogenesis and the interactions of p53 with related transcription factors (p73, p63).

[A model of enzymatic decarboxylation of glutamic acid]. / Model' fermentativnogo dekarboksilirovaniia glutaminovoi kisloty.

Interaction of glutamate decarboxylase with its adequate substrate and some quasi-substrates was studied by spectrokinetic, quantum-chemical and some other approaches. It was shown that in the course of decarboxylation an abortive transamination of pyridoxal-5'-phosphate leading to the enzyme inactivation does occur. Identification of intermediate coenzyme-substrate complexes allowed to formulate a model of enzymatic decarboxylation taking into account both the main and abortive reactions. The analysis of electronic structure of the intermediates revealed some of the factors determining the functional specificity of the reaction under study.