Modulatory effect of rRNA synthesis and ppUL83 nucleolar compartmentalization on human cytomegalovirus gene expression in vitro.
The nucleolus is a nuclear domain involved in the biogenesis of ribosomes, as well as in many other important cellular regulatory activities, such as cell cycle control and mRNA processing. Many viruses, including herpesviruses, are known to exploit the nucleolar compartment during their replication cycle. In a previous study, we demonstrated the preferential targeting and accumulation of the human cytomegalovirus (HCMV) UL83 phosphoprotein (pp65) to the nucleolar compartment and, in particular, to the nucleolar matrix of lytically infected fibroblasts; such targeting was already evident at very early times after infection. Here we have investigated the possible effects of rRNA synthesis inhibition upon the development of HCMV lytic infection, by using either actinomycin D or cisplatin at low concentrations, that are known to selectively inhibit RNA polymerase I activity, whilst leaving RNA polymerase II function unaffected. Following the inhibition of rRNA synthesis by either of the agents used, we observed a significant redistribution of nucleolar proteins within the nucleoplasm and a simultaneous depletion of viral pp65 from the nucleolus; this effect was highly evident in both unextracted cells and in nuclear matrices in situ. Of particular interest, even a brief suppression of rRNA synthesis resulted in a very strong inhibition of the progression of HCMV infection, as was concluded from the absence of accumulation of HCMV major immediate-early proteins within the nucleus of infected cells. These data suggest that a functional relationship might exist between rRNA synthesis, pp65 localization to the nucleolar matrix and the normal development of HCMV lytic infection.
Arcangeletti
Maria-Cristina
MC
Microbiology Section, Department of Pathology and Laboratory Medicine, University of Parma, Parma, Italy. mariacristina.arcangeletti@unipr.it
Rodighiero
Isabella
I
De Conto
Flora
F
Gatti
Rita
R
Orlandini
Guido
G
Ferraglia
Francesca
F
Motta
Federica
F
Covan
Silvia
S
Razin
Sergey V
SV
Dettori
Giuseppe
G
Chezzi
Carlo
C
D000704:Analysis of Variance; D002458:Cell Fractionation; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism* / Q000648:ultrastructure / Q000821:virology; D003587:Cytomegalovirus / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D054884:Host-Pathogen Interactions / Q000187:drug effects; D006801:Humans; D015530:Nuclear Matrix / Q000378:metabolism* / Q000648:ultrastructure / Q000821:virology; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D014763:Viral Matrix Proteins / Q000378:metabolism*
D009687:Nuclear Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D010750:Phosphoproteins; D012335:RNA, Ribosomal; D014763:Viral Matrix Proteins; C065418:cytomegalovirus matrix protein 65kDa