G2 checkpoint targets late replicating DNA

Abstract

In the multinucleate cells induced in Allium cepa L. meristems, the nuclei surrounded by the largest cytoplasm environment complete replication earlier (advanced nuclei), but have a longer G2, than the others (delayed nuclei). Thus, all nuclei break down the nuclear envelope and start metaphase simultaneously. The present report shows that this synchronization relies on a checkpoint mechanism. When completion of replication was prevented in the delayed nuclei (due to in vivo 5-aminouracil feeding initiated when the advanced nuclei were already in G2), the metaphase was also further delayed in the advanced ones. In turn, some of the delayed nuclei overrode the G2 checkpoint (adaptation) and entered into mitosis with broken chromatids (Del Campo et al., 1997). Anoxic UVA (313 nm) irradiation apparently prevents the binding of regulatory proteins to Br-DNA. The present report shows that late replicating sequences are the targets of the checkpoint signal produced by the still replicating nuclei. This signal delays metaphase in the advanced nuclei, whose DNA is already fully replicated. Thus, when the already replicated sequences of late replicating DNA was modified in the advanced nuclei by bromosubstitution followed by anoxic UVA irradiation, they entered into mitosis without any delay, ignoring the inhibitory signals produced by the still replicating nuclei.

FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular geometry of biomolecule 5-aminouracil

“…5-AU has been used as a starting material for the synthesis of other pyrimidines [2][3][4] or transition metal complexes [5]. The compatibility of 5-AU has been recognized in the central position of a DNA triplex [6], causing damage in the genome [7] or mitotic cell division [8,9].…”

Cytogenetic and Biochemical Responses of Wheat Seeds to Proton Irradiation at the Bragg Peak

“…The alteration of normal function of some proteins that ensure the optimal organization of nuclear chromatin can increase its adhesiveness, leading to abnormal metaphases and anaphases, chromosomal bridges and, finally, the inhibition of cytokinesis with formation of binucleated cells [ 43 ]. Giant cells may be polyploid cells that have occurred through alteration of microtubule organization and cytokinesis progress [ 44 , 45 ]. C-mitosis is the colchicine-like metaphase that occurs as a result of blocking the progression of metaphase to anaphase by inactivating of the spindle formation and, consequently, the cell becomes polyploid [ 46 , 47 ].…”

Eidetic Analysis of the Premature Chromosome Condensation Process

“…Its functions are connected with the assessment of internal and external conditions of the cell environment during mitosis and cytokinesis. PCP2 controls if the replication of DNA is properly terminated and also monitors the integrity of chromatin structure before its mitotic condensation (Del Campo et al, 2003). The checkpoint pathways functioning in G1 and G2 phases of cell cycle constitute however only part of the complex system formed by checkpoint mechanisms of the whole cell cycle (Bucher & Britten, 2008).…”