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Molecular and Cellular Biology, January 2000, p. 42-53, Vol. 20, No. 1
Centre d'Immunologie de Marseille-Luminy,
Institut National de la Santé et de la Recherche
Médicale-Centre National de la Recherche Scientifique, 13288 Marseille,1 and Laboratoire de
Génétique Médicale et Développement,
Faculté de Médecine, Institut National de la Santé et
de la Recherche Médicale, 13385 Marseille,2 France
Received 9 July 1999/Returned for modification 3 August
1999/Accepted 23 September 1999
V(D)J recombination in differentiating lymphocytes is a highly
regulated process in terms of both cell lineage and the stage of cell
development. Transgenic and knockout mouse studies have demonstrated
that transcriptional enhancers from antigen receptor genes play an
important role in this regulation by activating cis-recombination events. A striking example is the T-cell
receptor
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Definition of a T-Cell Receptor
Gene Core
Enhancer of V(D)J Recombination by Transgenic Mapping
-chain (TCR
) gene enhancer (E
), which in the mouse
consists of at least seven nuclear factor binding motifs (
E1 to
E7). Here, using a well-characterized transgenic recombination
substrate approach, we define the sequences within E
required for
recombination enhancer activity. The E
core is comprised of a
limited set of motifs (
E3 and
E4) and an additional previously
uncharacterized 20-bp sequence 3' of the
E4 motif. This core element
confers cell lineage- and stage-specific recombination within the
transgenic substrates, although it cannot bypass the suppressive
effects resulting from transgene integration in heterochromatic
centromeres. Strikingly, the core enhancer is heavily occupied by
nuclear factors in immature thymocytes, as shown by in vivo
footprinting analyses. A larger enhancer fragment including the
E1
through
E4 motifs but not the 3' sequences, although active in
inducing germ line transcription within the transgenic array, did not
retain the E
recombinational activity. Our results emphasize the
multifunctionality of the TCR
enhancer and shed some light on the
molecular mechanisms by which transcriptional enhancers and associated
nuclear factors may impact on cis recombination, gene expression, and
lymphoid cell differentiation.
*
Corresponding author. Mailing address: Centre
d'Immunologie INSERM-CNRS de Marseille-Luminy, Case 906, 13288 Marseille Cedex 9, France. Phone: (33) 491-269435. Fax: (33)
491-269430. E-mail: ferrier{at}ciml.univ-mrs.fr.
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