A Guide to the Russian Academy of Sciences - University of Texas ...

In 1995 studies in the Cell Proliferation Laboratory have been carried out in three main
directions: 1. Studies on the novel biological activities acquired by p53 mutants
continued. Upon introduction into the cell lines devoid of endogenous p53 gene
expression the mutant forms of p53 are able to increase frequency of gene
amplifications. The subtraction cloning was been carried out to identify novel genes
activated in response to mutant p53. A library of cDNAs expressed in response to
His175 mutant p53 was constructed and analyzed. Four types of cloned genes most
frequently represented in the library were identified and sequenced. The first type
corresponds to the gene coding for nucleolar protein No38. The second
corresponds to the gene encoding p21, the translationally-regulated protein
characteristic of some transformed cells. The third gene was, previously cloned and
sequenced from the brain cDNA library, although the product coded by this gene is
still unknown. The fourth gene was not previously identified or analysed. Northern
hybridization has shown that the expression of all four types of mRNA is activated
in response to mutant p53s, although some of them are also expressed upon the
wild-type p53 hyperexpression. At present a search for the corresponding response
elements mediating induction of these genes is under way. Besides, the s tudies of
biological activities of the full-length cDNAs of the newly identified genes are in
progress. 2. To identify functionally important domains of p53 gene the screening
of Genetic Suppressor Elements (GSEs) from the library of short random
fragments of p53 cDNA expressed as a part of a retroviral construct was carried
out. Such short fragments are able to interfere with p53 functions due either to short
peptides acting in a dominant-negative fashion, or to anti-sense RNA. Several types
of GSEs have been selected that are capable to immortalize primary fibroblasts, and
confer the resistance to the DNA-damaging drug etoposide. The GSEs were
mapped along the p53 cDNA. Four descrete functionally significant regions on the
p53 cDNA were identified in these experiments. At present further studies of cell
lines expressing these types of GSEs are carried out along with the elucidation of
the mechanisms of their action. 3. The cells transformed by activated oncogene Nras
express elevated levels of p53 protein. This elevation is due to transcriptional
activation of p53 gene. In primary cells such increase level causes arrest of the cell
cycle. In immortalized cells elevation of p53 has no effect on growth parameters.
Therefore, p53 gene may have a safeguard function by restriction of growth of the
cells with activated oncogenes. At present, studies on the effect of other dominant
oncogenes on p53 gene activity are in progress.
In 1992, there were at least five major research groups or units--a number which exceeded
seven in 1997:
(l.) The Genome Molecular Organization Group under Nikolai A. Tchurikov, D.
Bio. S., graduated from the Stavropol Medical Institute in 1972, and joined the
institute as a probationer in 1972. He defended his thesis on the detection and
properties of the gene Dm225--the mobile dispersed Drosophila element in 1977.
His current interest are in the molecular and genetic analysis of mobile elements, 5’
and 3’ regulatory elements in the expression of Drosophila genes, higher order
structure in Drosophila and human chromosomes, and in the physical and biological
analysis of parallel DNA.9
1997 update: GENOME ORGANIZATION
Head Nickolai A. Tchurikov, M.D., Ph.D., D.Sc.
Our work in 1995 was mainly concerned with two current projects: The study of domains
in eukaryotic chromosomes Earlier we described in Drosophila, human and plant
cells regular domains incorporating 50-150 kb DNA stretches (forum-domains,
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