proponent research area title summary

B.Colonna – Research proposal FIPFCB 2005
PROPONENT
Prof. Bianca COLONNA
Associate Professor of General Microbiology
Dipartimento di Biologia Cellulare e dello Sviluppo
Sezione di Scienze Microbiologiche
Università di Roma “La Sapienza”
Via dei Sardi 70
00185 ROMA (Italy)
tel (+39) 0649917580, 0649917582
fax (+39) 0649917594
email [email protected]
RESEARCH AREA
Molecular biology of microorganisms and viruses.
TITLE
Deciphering the complexity of virulence gene networks in Shigella and enteroinvasive Escherichia coli (EIEC):
the interplay among nucleoid proteins, promoter DNA structure and regulatory factors.
SUMMARY
The growing availability of bacterial genome sequences has substantiated the hypothesis that the regulation
of gene expression is the evolutionary response to the challenge of surviving in changing environments. This view
is strengthened by the observation that the complexity of an organism’s regulatory circuitry depends on the
complexity of its environment. Enteric bacteria, like E.coli, Shigella and Salmonella, which live in complex
environments have evolved correspondingly intricate control systems. Expression of virulence determinants is
integrated in layers of iterative regulatory networks to ensure a coordinated and on time synthesis of all
determinants necessary to induce the pathogenicity process. Like in other life-threatening human pathogens, also
in Shigella and EIEC the entry from the outer environment into the warmer host milieu is one of the central cues
triggering the expression of virulence factors. The plasmid regulatory cascade of Shigella represents an interesting
system to understand how pathogenic bacteria have evolved to prevent wasteful expression of the virulence
factors while ensuring strong and appropriate activation when this is required. It is increasingly evident that the
key to these sophisticate control/response systems mainly resides in the initiation of transcription. Thus
deciphering the events occurring around a virulence gene promoter in response to host environmental stimuli - in
terms of interplay among nucleoid proteins, promoter DNA structure and regulatory factors - is central to the
understanding of the pathogenicity mechanisms.
This proposal aims at a deeper comprehension of the molecular strategies adopted by the pINV virulence
gene promoters of Shigella and EIEC to process a variety of physicochemical signals coming from the
environment in order to trigger an on/off decision. In particular we want to investigate on the molecular
mechanisms by which protein-DNA interactions, protein-protein interactions, and chromatin structure integrate to
control the expression of virulence determinants turning them on and off at the right time and in the right place.
Morerover, we would like to understand which regulatory changes have followed, in the evolutionary transition
from E.coli to Shigella, the uptake of virulence genes so as to insert them into a regulatory network allowing for
an efficient host-environment-mediated expression.
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B.Colonna – Research proposal FIPFCB 2005
◊ Falconi, M., Prosseda, G., Giangrossi, M., Beghetto, E., Colonna, B. 2001 Involvement of FIS on the H-NS
mediated regulation of the virF gene of Shigella and Escherichia coli EIEC. Mol.Microbiol. 42:439-452
◊ Hommais, F., Krin, E., Laurent-Winter, C., Soutourina, O., Malpertuy, A., LeCaer, J.P., Danchin, A., Bertin,
P. 2001. Large-scale monitoring of pleiotropic regulation of gene expression by the prokaryotic nucleoidassociated protein, H-NS. Mol.Microbiol. 40:20-36
◊ Jin, Q., Yuan, Z., Xu, J., Wang, Y., Shen, Y., Lu, W., Wang, J., Liu, H., Yang, J., Yang, F. 2002. Genome
sequence of Shigella flexneri 2a: insights into pathogenicity through comparison with genomes of Escherichia
coli K12 and O157. Nucleic Acids Res. 30:4432-4441
◊ Karimova, G., Ullmann, A., Ladant, D. 2000. A bacterial two hybrid system that exploits a cAMP signaling
cascade in Escherichia coli. Methods Enzymol. 328:59-73
◊ Lan, R., Reeves, P.R. 2002. Escherichia coli in disguise: molecular origins of Shigella. Microbes Infect.
4:1125-1132
◊ Le Gall, T., Mavris, M., Martino, M.C., Bernardini, M.L., Denamur, E., Parsot, C. 2005. Analysis of virulence
plasmid gene expression defines three classes of effectors in the type III secretion system of Shigella flexneri.
Microbiology 151:951-962
◊ Madrid, C., Nieto, J.M., Paytubi, S., Falconi, M., Gualerzi, C.O., Juarez, A. 2002. Temperature-and H-NSdependent regulation of a plasmid-encoded virulence operon expressing Escherichia coli haemolyisin.
J.Bacteriol. 184:5058-5066
◊ McAdams, H.H, Srinivasan, B., Arkin, A.P. 2004. The evolution of genetic regulatory systems in bacteria.
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◊ Maurelli, A.T., Fernandez, R.E., Block, C.A., Rode, C.K., Fasano, A. 1998. Black hole and bacterial
pathogenitcity: a large genomic deletion that enhances the virulence of Shigella spp and enteroinvasive E.coli.
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◊ Perez-Martin, J., de Lorenzo, V. 1997. Clues and consequences of bending in transcription.
Annu.Rev.Microbiol. 51:593-628
◊ Porter, M.E., Dorman, C.J. 2002. In vivo DNA-binding and oligomerization properties of the Shigella flexneri
AraC-like transcriptional regulator VirF as identified by random and site specific mutagenesis. J.Bacteriol.
184:531-539
◊ Prosseda G., Fradiani, P.A., Di Lorenzo, M., Falconi, M., Micheli, G., Casalino, M., Nicoletti, M., Colonna, B.
1998. A role for H-NS in the regulation of the virF gene of Shigella and enteroinvasive Escherichia coli.
Res.Microbiol. 149:15-25
◊ Prosseda, G., Falconi, M., Nicoletti, M., Casalino, M., Micheli, G., Colonna, B. 2002. Histone-like proteins
and the Shigella invasivity regulon. Res. Microbiol. 153:461-468
◊ Prosseda, G., Falconi, M., Giangrossi, M., Gualerzi, C.O., Micheli, G., Colonna, B. 2004 The virF promoter in
Shigella:more than just a curved DNA stretch. Mol.Microbiol. 51:523-537
◊ Rohde, J.R., Luan, X., Rohde, H., Fox, J.M., Minnich, S.M. 1999. The Yersinia enterocolitica pYV virulence
plasmid contains multiple intrinsic DNA bends which melt at 37°C. J.Bacteriol. 181:4198-4204
◊ Samartizou, H., Mehrazin, M., Xu, Z., Benedik, M.J., Delcour, A.H. 2003. Cadaverine inhibition of porin
plays a role in cell survival at acid pH. J.Bacteriol. 185:13-19
◊ Sansonetti, P. J. 2001. Rupture, invasion and inflammatory destruction of the intestinal barrier by Shigella,
making sense of prokaryote-eukaryote cross-talks. FEMS Microbiol.Rev. 25:3-14
◊ Tendeng C., Bertin, P.N. 2003. H-NS in Gram-negative bacteria: a family of multifaceted proteins. Trends
Microbiol. 11:511-8
◊ Tobe, T., Yoshikawa, M., Mizuno, T., Sasakawa, C. 1993. Transcriptional control of the invasion regulatory
gene virB of Shigella flexneri: activation by VirF and repression by H-NS. J.Bacteriol. 175:6142-6149
◊ Travers, A.A. 1995. DNA bending by sequence and protein. In Lilley, D.M.J. (ed.), DNA-protein: Structural
Interactions. Oxford University Press, New York, NY, pp. 49-75
◊ Travers, A, Muskhelishvili, G. 2005. Bacterial chromatin. Curr.Opin.Genet.Dev. 15:507-14
COLLABORATORS
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Dr.Gianni Prosseda - Researcher - Dept.Cell and Developmental Biol., Univ.La Sapienza, Roma (Italy)
Dr.Maria Carmela Latella - PhD student - Dept.Cell and Devel.Biol., Univ.La Sapienza, Roma (Italy)
Dr.Gioacchino Micheli - Senior Invest. - IBPM CNR Lab.Acidi Nucleici, c/o Univ.La Sapienza, Roma (Italy)
Prof.Mauro Nicoletti - Associate Professor of Microbiology - Dept.Biomed.Sci., Univ.Chieti, Chieti (Italy)
Prof.Mariassunta Casalino - Associate Professor of Microbiology - Dept.Biol., Univ. Roma III, Roma (Italy)
Prof.Claudio Gualerzi - Full Professor of Genetics - Dept.MCA, Univ.Camerino, Camerino (Italy)
Dr.Maurizio Falconi - Senior Investigator - Dept.MCA, Univ.Camerino, Camerino (Italy)
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