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Molecular biology of microorganisms and viruses - AREA 1
Polyomavirus-host interaction: role of the early phases of
infection in determining virus permissivity and role of PARP-1
in the regulation of immediate early gene expression
P a r t i c i p a n t s :
Rossella Maione, professor; Michaela Cavaldesi, research
fellow; Rosaria Carbone, Maddalena Caruso, Rocco
Figliola, post-doc fellows; Marianna Rossi, Anna Busanello,
PhD students; Olga Sthandier, technician.
C o l l a b o r a t i o n s :
Dipartimento di Biotecnologie Cellulari ed Ematologia, Sapienza-
Università di Roma (Prof. Paola Caiafa); Dipartimento di
Medicina Sperimentale, Sapienza-Università di Roma (Dr.
Massimo Gentile); The Burnham Institute, La Jolla, CA, USA
(Prof. Robert Liddington); Department of Microbiology,
University of Buenos Aires School of Medicine, Buenos Aires,
Argentina (Prof. Norberto Sanjuan).
Report of activity
Since many years we have been interested in the
study of the biology of the murine Polyomavirus
(Py). Py has been successfully used as a model system
for the study of the mechanisms regulating replication,
gene expression, tumor induction and, more
recently, the initial virus-host cell membrane interactions.
Our research has been focused on the central
role played by the major capsid protein VP1 in the
early phases of viral infection, including cell recognition,
entry, formation of early transcription complexes
and cell cycle activation. A second subject,
originally branched from the study of the modifications
of viral chromatin during the early response,
concerns the role of Poly(ADP-ribose)polymerases
(PARPs) in cell cycle re-entry. A third subject, initially
stemmed from our interest in the oncogenic
properties of Py, is related to the interdependence of
cell cycle and differentiation in the muscle model.
The most significant results concern the following
topics:
Principal investigator: Paolo Amati
Professor of Molecular Genetics
Dipartimento di Biotecnologie Cellulari ed Ematologia
Sezione di Genetica Molecolare
Tel: (+39) 06 490393; Fax: (+39) 06 4462891
amati@bce.uniroma1.it
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Role of virus-host cell receptor(s) interaction
in determining the virus tissue tropism and
tumorigenicity
We have previously shown that Py cell entry into
fibroblasts is a multi-step process involving the
attachment to primary sialic acids-containing cell
receptor(s) and post-binding interaction with secondary
receptor(s), such as the α4β1 integrin,
through the VP1-LDV motif. However, the role of
Py-receptor(s) interaction in virus tissue-tropism
and tumorigenicity in vivo remained to be more
clearly understood. By studying a recombinant
mutant, PyLNV, with a single aa substitution in the
VP1-LDVmotif (D138N), we have shown that
mutation in this motif affects Py infectivity and conditions
virus tissue tropism in vivo. Indeed, although
not critical for virus viability, the D138N substitution
abrogates the post-attachment Py−α4β1 interaction,
rendering the PyLNV mutant virus twofold
less infectious than the Py wild type (Wt) in α4β1positive
fibroblasts. Moreover, when inoculated in
newborn C57BL/6 mice, PyLNV showed an altered
spectrum of in vivo replication compared with
PyWt, particularly in the skin and in the kidney
(Caruso et al., 2007).
Further analysis of the role of Py- α4β1 interaction
in tissue tropism and tumorigenicity has been performed
in collaboration with Prof. N. Sanjuan.
Newborn C3H Bittner-Dawe mice were sub-cutaneously
inoculated with PyLNV or PyWt, sacrificed
at different days post infection to analyse the distribution
of VP1 in different organs/tissues. No differences
were observed in the ability of dissemination
of both strains, neither in the involved organs, nor
in the intensity of the immunolabeling.
Surprisingly, both viruses infected the kidneys
throughout the experiment, initially in the interstitial
cells of the medulla and then in the tubules. The
incidence of neoplasia for both viruses was about