chimeric rat (human) HMGB1 and HMGB2 with switched acidic
C-tails. These authors have demonstrated that HMGB1 with the
longest acidic tail was less effective than HMGB2a and 2b with
shorter C-tails (at a given molar input ratio) in DNA supercoiling
and in inducing T4 ligase-mediated circularization of an 88-bp
DNA fragment. While removal of the acidic tails increased the
affinity of the HMG-boxes for DNA, it completely abolished the
differences between the three HMGB species (Lee and Thomas,
2000). Thus, the length and very likely also the sequence (Fig. 1B,
see also Payet and Travers, 1997; Ueda et al., 2004) of the acidic
tail appears to be the dominant factor in mediating the differences
in DNA binding properties among evolutionarily distinct
HMGB1 proteins to fulfill their different cellular roles. The
ability of HMGB1 protein to bend (and untwist) DNA, and to
physically interact with plethora of transcription factors and other
sequence-specific proteins, is the most plausible explanation of
functioning of HMGB1 in facilitation of DNA recombination and
transcription by promoting binding of these factors to their
cognate sites, and enabling communications of distant regulatory
elements by DNA looping (reviewed by Thomas and Travers,
2001; Agresti and Bianchi, 2003).
After this paper was submitted for publication, a report on
cloning and characterization of HMGB1 from S. mansoni and S.
haematobium was published (Gnanasekar et al., 2006). The
authors concluded that SmHMGB1 is a stage-specific protein,
being abundantly expressed in eggs and adult female stages, and
at moderate levels in skin-stage schistosomula. Whereas the main
focus of our paper is DNA binding properties of the SmHMGB1
protein, the paper of Gnanasekar et al. (2006) describes possible
pro-inflammatory functions of the parasite derived HMGB1
protein. SmHMGB1 was shown to be a potent inducer of a
number of pro-inflammatory cytokines such as TNFα,IL-1Rα,
IL-13 and MIP-1α from mouse peritoneal macrophages. Release
of pro-inflammatory cytokines by SmHMGB1 seemed to be
associated with the domain B of the protein, and anti-SmHMGB1
antibodies blocked the SmHMGB1-induced TNFα secretion from
mouse macrophages. As both TNFα and IL-13 represent critical
molecules in the development of egg-induced pathology of
schistosomias (e.g. Haseeb et al., 2001), it is likely that egg-
derived SmHMGB1 may have an important immunomodulatory
role in the development of egg-induced pathology and granuloma
responses in schistosomias.
The (nuc lear and extracellular) role of SmHMGB1 or
SjHMGB1 proteins (as well as other, not yet identified, proteins
of the HMGB-box family) remains to be established in the
complex cellular processes of the helminths S. mansoni and S.
japonicum. Knowledge about these processes would signifi-
cantly strengthen the ongoing efforts associated to functional
genomics with data derived from whole genome projects of S.
mansoni and S. japonicum which are near completion (El-Sayed
et al., 2004; Lukeš et al., 2005).
Acknowledgements
We would like to thank Dr. Jennifer Fitzpatrick (University of
Cambridge) for preparing S. japonicum cDNA. The technical
assistance of Maria Marta Freire is also acknowledged. M.R.F. is a
recipient of CNPq fellowship. This research received financial
support from UNDP/World bank/World Health Organization/
TDR, Conselho Nacional de Desenvolvimento Científico e Tec-
nológico, CNPq-PROFIX No. 540002/01-1 (CAPES — Coor-
denação de Aperfeiçoamento de Pessoal de Nível Superior), by
the international collaboration program between Brazilian
Academy of Sciences and the Academy of Sciences of the
Czech Republic, and by grants to M.Š. from the Academy of
Sciences of the Czech Republic (AVOZ50040507: Biophysics of
dynamic structures of biological systems) and the Grant Agency
of the Czech Republic (204/05/2031). Finally, we would like to
thank an anonymous reviewer for his critical comments which
helped improve the quality of the final version of the manuscript.
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