Evidence of a differential organization of chromatin containing terminal or interstitial (TTAGGG)n repeats by in situ digestion with nucleases.
(TTAGGG)n sequence repeats in human telomeres and in Chinese hamster interstitial centromeric areas were digested in situ with exonuclease III (ExoIII) and exonuclease Bal 31. Incubation with AluI was performed beforehand to increase DNA breaks near telomere sequence areas. DNA removal at these specific regions was quantified by digital image analysis of the fluorescence in situ hybridization signal produced by a telomeric probe. Exonuclease III was 2.6 times more active in interstitial than in terminal telomeric sequence areas. Exonuclease Bal 31 was 2.3 times more effective in terminal than in interstitial telomeric sequence regions. These results support the hypothesis that chromatin is differentially organized in both telomeric sequence areas, despite their similar DNA composition.
Fernández
J L
JL
Laboratorio de Genética Molecular y Radiobiología, Centro Oncológico de Galicia, La Coruña (Spain). genetica<fcog@jet.es
Goyanes
V J
VJ
Ramiro-Díaz
J
J
Gosálvez
J
J
D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002843:Chromatin / Q000235:genetics*; D006224:Cricetinae; D015252:Deoxyribonucleases, Type II Site-Specific; D005090:Exodeoxyribonucleases; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008214:Lymphocytes; D012091:Repetitive Sequences, Nucleic Acid; D016615:Telomere / Q000235:genetics*
D002843:Chromatin; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; C024669:endodeoxyribonuclease AluI; D015252:Deoxyribonucleases, Type II Site-Specific