title: Molecular organization of internal telomeric sequences in Chinese hamster chromosomes.
abstract: In Chinese hamster extended blocks of telomeric-like repeats were previously detected by in situ hybridization at the pericentromeric region of most chromosomes and short arrays were localized at several interstitial sites. In this work, we analyzed the molecular organization of internal telomeric sequences (ITs) in the Chinese hamster genome. In genomic transfers hybridized with a telomeric probe, multiple Bal31 insensitive fragments were detected. Most of the fragments ranged in size between less than 1 kb and more than 100 kb and some were polymorphic. Fluorescence in situ hybridization experiments on DNA fibers and on elongated chromosomes showed that the pericentromeric ITs are composed of extensive and essentially continuous arrays of telomeric-like sequences. We then isolated three genomic regions which contain short ITs. These ITs are localized at interstitial sites (3q13-15, 3q21-26, 1p26) and are composed of 29-126 bp of (TTAGGG)(n) repeats. A peculiar feature of all the three ITs is the AT richness of the flanking sequences. Since AT-rich DNA is known to be unstable and characteristic of several mammalian fragile sites, we propose that the three ITs were inserted at these sites during the repair of double strand breaks.
authors.affiliation: Dipartimento di Genetica e Microbiologia "A. Buzzati-Traverso", Università degli Studi di Pavia, via Ferrata 1, 27100, Pavia, Italy.
authors.forename: Maura
authors.initials: M
authors.lastname: Faravelli
authors.forename: Claus M
authors.initials: CM
authors.lastname: Azzalin
authors.forename: Livia
authors.initials: L
authors.lastname: Bertoni
authors.forename: Olga
authors.initials: O
authors.lastname: Chernova
authors.forename: Carmen
authors.initials: C
authors.lastname: Attolini
authors.forename: Chiara
authors.initials: C
authors.lastname: Mondello
authors.forename: Elena
authors.initials: E
authors.lastname: Giulotto
mesh_terms: D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics*; D003001:Cloning, Molecular; D006224:Cricetinae; D004247:DNA / Q000737:chemistry / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000235:genetics*
chemical_list: D004247:DNA