Induction of distamycin A-inducible rare fragile sites and increased sister chromatid exchanges at the fragile site

Abstract

Expression of distamycin A-inducible rare fragile sites by AT-specific DNA-ligands was examined in lymphoblastoid cell lines derived from heterozygous carriers for the fra(8)(q24), fra(16)(p12), and fra(16)(q22) sites. The sensitivity of fragile site expression to the inducers was different at these fragile sites. The expression of fra(8)(q24) was induced markedly by Hoechst 33258, but not by distamycin A or berenil. An increased expression of fra(16)(p12) was found following treatment with Hoechst 33258 or berenil, but not with distamycin A. At fra(16)(q22), distamycin A markedly induced the fragile site, but Hoechst 33258 and berenil did not. Since their response to the different inducers was similar to that found in cultured lymphocytes, lymphoblastoid cell lines appear to retain their inherent properties. Although BrdUrd alone did not induce any fragile sites, concomitant treatment with BrdUrd plus the inducer was synergistically effective in inducing all the fragile sites. An increased frequency of sister chromatid exchanges was observed at fra(16)(p12) following simultaneous treatment with BrdUrd and berenil, mainly when the site was expressed as an isochromatid gap. Thus, the induced fra(16)(p12) site is a hot spot for the formation of sister chromatid exchanges, as found in other reported fragile sites.

Cytogenetic Studies of Berenil in Mice

“…An increased frequency of SCEs was observed following simultaneous treatment with bromodeoxyuredine and Berenil, mainly when the site was expressed as an isochromatid gap. Thus, the induced Frg (16) (P12) site is a hot spot for the formation of SCEs as found in other reported fragile sites (Schmid et al 1986, Tsuji et al 1991, Felbor 2003.…”

Induction of a BrdU-enhanceable fragile site-like lesion and sister chromatid exchanges at 11q23.1 in EBV-transformed lymphoblastoid cell lines

“…Recently. Tsuji et al (1991) reported that in EBV-transformed LCLs the incidence of SCE formation at fra( 16) (p 12) was 18.5 % and SCEs occurred at the fragile site only when the sites were expressed. The fra( 16) (p 12) was shown to be a new distamycin A-inducible rare fragile site and present only in a single Japanese population (Hecht, 1988;Sutherland and Ledbetter, 1989).…”

“…By applying EBV-trans formed LCLs derived from fragile site carriers. Tsuji et al (1991) have also demonstrated that the induced fragile site at 16p 12 was a hot spot for the formation of SCEs. These data suggest that the rare and common fragile sites may act as predis posing factors for chromosome instability and somatic recombi nation.…”

“…Three LCLs, D-3 (16q22), L-277-1 ( 16p 12.1). and HeD-5 (8q24.1), were obtained by EBV-transformation of the lymphocytes of fragile site carriers described previously : Tsuji et al, 1991. Four LCI-s (AT-1.…”

Fragile sites, chromosomal lesions, tandem repeats, and disease

“…Advances in understanding the formation and resolution of SCEs, the factors involved, their involvement in genome instability, and under-replicated regions (as observed at FRAXA ( Kerem et al, 1988 )), all will improve our understanding of the association of SCEs with fragile sites ( Baxter, 2015 ; Broderick and Niedzwiedz, 2015 ; Uchiyama and Fukui, 2015 ). CFSs are sites of preferential SCE, regardless of whether a visible gap exists concurrently with the SCE ( Glover and Stein, 1987 ; Schmid et al, 1987 ; Feichtinger and Schmid, 1989 ; Hirsch, 1991 ; Lukusa et al, 1991 ; Tsuji et al, 1991 ).…”