Induction of a G ₁ -S checkpoint in fission yeast

Abstract

Entry into S phase is carefully regulated and, in most organisms, under the control of a G 1 -S checkpoint. We have previously described a G 1 -S checkpoint in fission yeast that delays formation of the prereplicative complex at chromosomal replication origins after exposure to UV light (UVC). This checkpoint absolutely depends on the Gcn2 kinase. Here, we explore the signal for activation of the Gcn2-dependent G 1 -S checkpoint in fission yeast. If some form of DNA damage can activate the checkpoint, deficient DNA repair should affect the length of the checkpoint-induced delay. We find that the cell-cycle delay differs in repair-deficient mutants from that in wild-type cells. However, the duration of the delay depends not only on the repair capacity of the cells, but also on the nature of the repair deficiency. First, the delay is abolished in cells that are deficient in the early steps of repair. Second, the delay is prolonged in repair mutants that fail to complete repair after the incision stage. We conclude that the G 1 -S delay depends on damage to the DNA and that the activating signal derives not from the initial DNA damage, but from a repair intermediate(s). Surprisingly, we find that activation of Gcn2 does not depend on the processing of DNA damage and that activated Gcn2 alone is not sufficient to delay entry into S phase in UVC-irradiated cells. Thus, the G 1 -S delay depends on at least two different inputs.

Sirtuin 7 promotes cellular survival following genomic stress by attenuation of DNA damage, SAPK activation and p53 response

“…In addition it is also a key step in maintaining genomic integrity for accurate DNA strand replication [32,33]. In view of this, we evaluated if delayed G1 to S-phase transition during cell cycle also translates to an increased tolerance to genomic stress using DNA 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 Fig.…”

Cell-Cycle Analyses Using Thymidine Analogues in Fission Yeast

“…Furthermore, this lack of detection confirms our previous data demonstrating a G1/S checkpoint in S. pombe induced by UV light. We have previously shown that this dose of UV-irradiation induces 0.2–0.3 CPD per kb of DNA [27]. Considering that the fission yeast genome is about 13,8 Mb and that a minimum of 30 nucleotides are synthesized for each CPD, we estimate that at least 10 5 nucleotides can be incorporated after UV-irradiation.…”

GCN2, an old dog with new tricks

“…DNA-PK interacts with DNA doublestrand breaks and a wide diversity of irregular DNA substrates, and co-operates with ATR (ataxia telangiectasiaand Rad3-related) and ATM (ataxia telangiectasia mutated) to phosphorylate DNA-damage checkpoint proteins [21,22]. However, in UVC-irradiated fission-yeast cells, Gcn2 is activated regardless of the repair capacity of the cells [23]. However, in UVC-irradiated fission-yeast cells, Gcn2 is activated regardless of the repair capacity of the cells [23].…”