ACTIVATION OF rDNA TRANSCRIPTION FOLLOWING HUMAN EMBRYO FIBROBLAST INFECTION WITH
CYTOMEGALOVIRUS IN VITRO
O. O. Zharskaya,1 A. S. Barsukova,1 A. A. Medzhidova, 2
N. E. Fedorova,2 Kushch A.A.,2 O. V. Zatsepina 1, 3 *
1 The A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University,
2 the D. I. Ivanovsky Research Institute of Virology RAMS, and 3 the M. M. Shemaykin-Yu.
A. Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow;
* e-mail: zatsepina_olga@mail.ru
Cytomegalovirus (CMV) infection of human diploid embryo fibroblasts in vitro causes a massive cell death on the
3-4th day of infection with a high primary infection coefficient (1-5 U/cell). Cytopathological effects
of viral infection on the 3-4th day includes diminishes of the cell size, changes in their form,
compaction of the nuclear chromatin, and disorganization and inactivation of the nucleolus. However, the early
stages of the viral infection progression (the 1st-2nd day) are accompanied by unequivocal
activation of rDNA (ribosomal gene) and the bulk of chromatin transcription. There are several features to support
this conclusion: in the early CMV-infected cell 1) the nucleolar size is increased; 2) the number of intranucleolar
foci binding the specific RNA-polymerase I transcription factor (UBF) is augmented; 3) the Ag-NOR staining is
enhanced; 4) 3H-uridine incorporation to the nucleoli is activated; 5) the ultrastructure of the
nucleolus is changed. Altogether, these data argue in favor of activation of rDNA transcription in human
fibroblasts in vitro at the initial stages of infection.
Key words: human Cytomegalovirus, nucleolus, rDNA, transcription
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