title: Cell cycle variations in chromatin structure detected by DNase I.
abstract: We have recently developed a reproducible method for the use of DNase I as a sensitive probe of chromatin structure (Prentice, D A & Gurley, L R, Biochim biophys acta 740 (1983) 134) [12] and have used this probe to investigate chromatin structure during the interphase of the cell cycle. Chinese hamster cells (line CHO) were synchronized by: (1) mitotic detachment, to obtain M-phase cells; (2) isoleucine deprivation, to obtain G1-phase cells; and (3) sequential use of isoleucine deprivation followed by release into the presence of hydroxyurea, to obtain cells blocked at the start of S phase. The cells were released from the various blocking schemes and nuclei were isolated and digested with DNase I at various times. The digestion kinetics were monitored to detect possible changes in chromatin condensation through the cell cycle. The chromatin was much more accessible to DNase I in G1 phase than in S or G2 phase, with only small variations in structure detected in late G1 and very early S phase. From early S phase up to mitosis, the chromatin became increasingly condensed and inaccessible to DNase I action. These results support the concept of a chromatin condensation cycle during interphase as well as during mitosis.
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002458:Cell Fractionation / Q000379:methods; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis / Q000648:ultrastructure; D002469:Cell Separation; D055598:Chemical Phenomena; D002621:Chemistry; D002843:Chromatin / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D003850:Deoxyribonuclease I; D005260:Female; D005434:Flow Cytometry; D007399:Interphase; D007532:Isoleucine / Q000502:physiology; D007700:Kinetics; D008938:Mitosis; D010053:Ovary
chemical_list: D002843:Chromatin; D007532:Isoleucine; D003850:Deoxyribonuclease I