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Molecular and Cellular Biology, April 1999, p. 3156-3166, Vol. 19, No. 4
Unité de Génétique
Moléculaire Murine,
Received 20 July 1998/Returned for modification 2 September
1998/Accepted 17 December 1998
X-chromosome inactivation in female mammals is controlled by the
X-inactivation center (Xic). This locus is required for inactivation in
cis and is thought to be involved in the counting process
which ensures that only a single X chromosome remains active per
diploid cell. The Xist gene maps to the Xic region and has
been shown to be essential for inactivation in cis.
Transgenesis represents a stringent test for defining the minimal
region that can carry out the functions attributed to the Xic. Although
YAC and cosmid Xist-containing transgenes have
previously been reported to be capable of cis inactivation
and counting, the transgenes were all present as
multicopy arrays and it was unclear to what extent individual copies
are functional. Using two different yeast artificial chromosomes
(YACs), we have found that single-copy transgenes, unlike multicopy
arrays, can induce neither inactivation in cis nor
counting. These results demonstrate that despite their large size and
the presence of Xist, the YACs that we have tested lack sequences critical for autonomous function with respect to X inactivation.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Xist Yeast Artificial Chromosome
Transgenes Function as X-Inactivation Centers Only in Multicopy
Arrays and Not as Single Copies
*
Corresponding author. Mailing address: Unité de
Génétique Moléculaire Murine, CNRS URA 1968, Institut
Pasteur, 25 rue du Docteur Roux, F-75724 Paris Cedex 15, France. Phone:
33 1 456 88653. Fax: 33 1 456 88656. E-mail:
eheard{at}pasteur.fr.
Molecular and Cellular Biology, April 1999, p. 3156-3166, Vol. 19, No. 4
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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