Results: 2

1.
Fig. 2.

Fig. 2. From: Checkpoint genes and Exo1 regulate nearby inverted repeat fusions that form dicentric chromosomes in Saccharomyces cerevisiae.

Pathways that prevent inverted repeat fusion. (A) Summary of different checkpoint pathways that prevent fusion of nearby inverted repeats and cell death. A stalled fork (purple cloud) leads to Mec1 activation and fork stabilization in Rad53-dependent (3) or -independent (1 and 2) manner. Mec1 acts via Rad9 and Chk1 to preserve stability (1). Rad53 and MRX prevent instability, and thus repeat fusion, by regulating the Exo1 nuclease (3 and 4). Rad53- and Exo1-mediated regulation of stability and prevention of inverted repeat fusion does not require Rad9 or Dun1 kinase. Rad53 signal amplification by Rad9 and Mrc1 is also dispensable for suppression of inverted repeat fusion. (B and C) Possible roles of Exo1. Faithful template switch to the newly replicated sister strand (B), and faulty template switch to a template that is made accessible by Exo1-dependent DNA degradation (C).

Salma Kaochar, et al. Proc Natl Acad Sci U S A. 2010 December 14;107(50):21605-21610.
2.
Fig. 1.

Fig. 1. From: Checkpoint genes and Exo1 regulate nearby inverted repeat fusions that form dicentric chromosomes in Saccharomyces cerevisiae.

Chromosome system to detect instability. (A) Two homologs of ChrVII and mutant alleles on each allow for genetic detection of chromosome changes. The CAN1 gene has been removed from ChrV and inserted into one copy of ChrVII. Selection for the loss of the CAN1 gene allows the growth of cells with any of three types of chromosome changes, including simple loss, allelic recombinants, and mixed colonies. Mixed colonies contain cells of multiple genotypes, including a specific translocation. See SI Materials and Methods for details. (B) Configuration of elements in the ChrVII403 site and the geometry and order of how fusion might occur. Two tRNA genes (pentagons) transcribe toward the oncoming fork and slow replication. Fusion between the two LTR σ repeats (S2 and S3), shown diagrammatically, forms a dicentric, followed by recombination between the two LTR δ sequences (D7 and D11) to form the specific translocation. (Reprinted from reference 10. Copyright © 2009 Cold Spring Harbor Laboratory Press.)

Salma Kaochar, et al. Proc Natl Acad Sci U S A. 2010 December 14;107(50):21605-21610.

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