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Early and late replicating DNA involved in the G 1 to S transition in Allium cepa L meristematic cells
Author(s) -
GonzalezFernandez Aurora,
Aller Patricio,
Sans Jorge,
Torre Consuelo
Publication year - 1992
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(92)90034-x
Subject(s) - biology , dna replication , cycloheximide , period (music) , meristem , dna synthesis , dna , transition (genetics) , genetics , population , mitosis , origin of replication , microbiology and biotechnology , gene , cell culture , physics , demography , sociology , acoustics
Summary— The involvement of portions of the genome replicated at different times of the S period in the regulation of the G 1 to S transition was analyzed in Allium cepa L meristem cells. For this, DNA bromosubstitution confined to discrete portions of a previous S period followed by anoxic UVA irradiation (300–400 nm light) was performed in synchronous cells. Sequences replicated in late S appeared to be involved in the positive regulation of the initiation of replication. Hence, cells were prevented from initiating replication if irradiated at mid G 1 only when the DNA sequences replicated in the last third of the previous S period were bromosubstituted. Cycloheximide‐induced inhibition of protein synthesis at late G 1 also prevented the G 1 to S transition. Sequences replicated in mid S appeared unrelated to any control of the initiation of replication. On the other hand, sequences replicated in the first third of the S period seemed to be involved in the negative regulation of the initiation of replication, since irradiation after previous bromosubstitution of early replicating DNA sequences advanced G 1 cells into the next S phase and increased the proliferative fraction of the population. Finally, the simultaneous inactivation of DNA sequences involved in both positive and negative regulation of replication allowed the cells to enter into S.