Cristina Martín-Castellanos

Spanish National Research Council | CSIC · Instituto de Biología Funcional y Genómica (IBFG)

Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to hundreds of times more frequently at special sites, called hot spots, than in other regions of the genome. What di...

A physical connection between each pair of homologous chromosomes is crucial for reductional chromosome segregation during the first meiotic division and therefore for successful meiosis. Connection is provided by recombination (crossing over) initiated by programmed DNA double-strand breaks (DSBs). Although the topoisomerase-like protein Spo11 mak...

Meiosis is a specialized nuclear division by which sexually reproducing diploid organisms generate haploid gametes. Recombination between homologous chromosomes facilitates accurate meiotic chromosome segregation and is initiated by DNA double-strand breaks (DSBs) made by the conserved topoisomerase-like protein Spo11 (Rec12 in fission yeast), but...

The study of meiosis regulation has always been carried out in parallel with mitotic cell cycle discoveries. The basic cell cycle machinery that regulates mitosis, based on fluctuations in the activity of cyclin-dependent kinases (CDKs), is responsible for the main transitions that occur during meiosis. However, the special characteristics of meios...

How eukaryotic cells control their duplication is a fascinating example of how a biological system self-organizes specific activities to temporally order cellular events. During cell cycle progression, the cellular level of CDK (Cyclin-Dependent Kinase) activity temporally orders the different cell cycle phases, ensuring that DNA replication occurs...

Cyclins and CDKs (Cyclin Dependent Kinases) are key players in the biology of eukaryotic cells, representing hubs for the orchestration of physiological conditions with cell cycle progression. Furthermore, as in the case of meiosis, cyclins and CDKs have acquired novel functions unrelated to this primal role in driving the division cycle. Meiosis i...

The S phase checkpoint is crucial to maintain genome stability under conditions that threaten DNA replication. One of its critical functions is to prevent Exo1-dependent fork degradation, and Exo1 is phosphorylated in response to different genotoxic agents. Exo1 seemed to be regulated by several post-translational modifications in the presence of r...

CDKs (cyclin-dependent kinases) associate with different cyclins to form different CDK-complexes that are fundamental for an ordered cell cycle progression, and the coordination of this progression with different aspects of the cellular physiology. During meiosis programmed DNA double-strand breaks (DSBs) initiate recombination that in addition to...

DSB formation is reduced in crs1 mutants (deficient DSB-repair condition, rad50S). (A) Detection of mbs1 breakage by Southern blot in control (CMC967) and crs1 deletion mutants (CMC1177) during synchronous meiosis of pat1-114 rad50S diploids. Percentage of breakage is represented on the right. (B) PFGE separation of entire chromosomes during the sa...

Analysis of meiotic progression in cig1, crs1, and cig1 crs1 deletion mutants. (A) Flow cytometry analysis of synchronous diploid pat1-114 meiosis of control (CMC7), cig1 (CMC1010), crs1 (CMC1059), and double cig1 crs1 (CMC1113) deletion mutants. DNA content (FL2-H) and cell size (FSC) histograms are shown. Dashed-lined box outlines premeiotic S-ph...

Untreated cdc2-asM17 mutants show a faster S-phase progression. (A) Flow cytometry analysis of synchronous diploid pat1-114 control (CMC7) and pat1-114 cdc2-asM17 (CMC1066) meiosis. Neither DMSO nor ATP-analog was added to the cells. DNA content (FL2-H) histograms are shown. (B) Quantification of chromosome segregation by DAPI staining and nuclear...

Proteins required for DSB formation. Essential proteins for DSB formation at meiotic hostpots are listed. Proteins are grouped based on the complexes they belong to (LinE, SFT, and DSBC-complexes). Names in parenthesis correspond to S. cerevisiae orthologs. Number and position of minimal and consensus CDK sites present in these proteins are indicat...

Recombination assays with rec7, rec14, rec10, and rec27 mutants in putative CDK phosphorylation sites. Crosses of h- ade6-M26 x h+ ade6-3049 homozygous for the different mutants were performed in MEA and plated for recombinant frequency at least twice. Tables on the right show gene conversion expressed as the mean of Ade+ per 104 viable spores +/-...

Analysis of meiotic progression in cig1, cig2, and cig1 cig2 deletion mutants. (A) Flow cytometry analysis of synchronous diploid pat1-114 meiosis of control (CMC7), cig1 (CMC1010), cig2 (CMC1022), and double cig1 cig2 (CMC1023) deletion mutants. DNA content (FL2-H) and cell size (FSC) histograms are shown. Dashed-lined box outlines premeiotic S-ph...

Chemical inhibition of Cdc2 blocks DSB formation in rad3 mutants (CDK inhibition after DNA replication). (A) On the left Flow cytometry analysis of synchronous haploid pat1-114 cdc2-asM17 rad3 meiosis (CMC1165) with DMSO (top left panel) or 20 μM 1-NM-PP1 (top right panel) added at 2 hr 15 min (arrow in the bottom panel) after meiotic induction of...

Spore viability of different cyclin deletion mutants. The same crosses as for the gene conversion assays in Fig 1 (h- ade6-M26 x h+ ade6-3049) were performed in MEA and spores plated twice in YES. Graph shows spore viability expressed as mean of the percentage relative to the control cross +/- SEM of 4 independent crosses based on the cumulative nu...

Qualitative recombination assays with single, double, and triple rec7, rec14 and rec27 mutants in putative CDK phosphorylation sites. Crosses of h- ade6-M26 x h+ ade6-3049 homozygous for the different mutants were performed in MEA and an equal number of spores (104 and serial 1/4 dilutions) plotted on YEA, YE+Guanine, MM+Adenine, and MM plates. A c...

Defective LinE maturation in double cig1 crs1 deletion mutants. Synchronous diploid pat1-114 rec25-GFP meiosis of control (CMC78) and double cig1 crs1 deletion mutants (CMC1207) were induced. (A) Meiotic progression. On the top Flow cytometry analysis showing DNA content (FL2-H) histograms. Dashed-lined box outlines premeiotic S-phase progression....

S. pombe strains. Alleles other than commonly used auxotrophies and mating type are ade6-3049 [115], ade6-M26 [116], pat1-114 [73], rad50S [72], cig2::ura4+ [117], rec25-204::GFP-kanMX6 [Rec25-GFP] [16], rec27-184::kanMX6 [65], cdc2-asM17 [74], and rad3::ura4+ [118, 119]. cig1::hphMX6, crs1::hphMX6, rec7::ura4+, rec7-cdk1, rec7-cdk2, rec7-cdk1cdk2,...

During Schizosaccharomyces pombe meiotic prophase, homologous chromosomes are co-aligned by linear elements (LinEs) analogous to the axial elements of the synaptonemal complex (SC) in other organisms. LinE proteins also promote the formation of meiotic DNA double-strand breaks (DSBs), the precursors of cross-overs. Rec10 is required for essentially...

Septation and spore formation in fission yeast are compartmentalization processes that occur during the mitotic and meiotic cycles, and that are regulated by the septation initiation network (SIN). In mitosis, activation of Sid2 protein kinase transduces the signal from the spindle pole body (SPB) to the middle of the cell in order to promote the c...

Trabectedin (Yondelis) is a potent antitumor drug that has the unique characteristic of killing cells by poisoning the DNA nucleotide excision repair (NER) machinery. The basis for the NER-dependent toxicity has not yet been elucidated but it has been proposed as the major determinant for the drug's cytotoxicity. To study the in vivo mode of action...

Meiosis is a specialized form of cell division by which sexually reproducing diploid organisms generate haploid gametes. During a long prophase, telomeres cluster into the bouquet configuration to aid chromosome pairing, and DNA replication is followed by high levels of recombination between homologous chromosomes (homologs). This recombination is...

Cell proliferation and patterning must be coordinated for the development of properly proportioned organs. If the same molecules were to control both processes, such coordination would be ensured. Here we address this possibility in the Drosophila wing using the Dpp signaling pathway. Previous studies have shown that Dpp forms a gradient along the...

During Drosophila development the cell cycle is subject to diverse regulatory inputs. In embryos, cells divide in stereotypic patterns that correspond to the cell fate map. There is little cell growth during this period, and cell proliferation is regulated at G2/M transitions by patterned transcription of the Cdk1-activator, Cdc25/String. The strin...

Eukaryotic cells coordinate cell size with cell division by regulating the length of the G1 and G2 phases of the cell cycle. In fission yeast, the length of the G1 phase depends on a precise balance between levels of positive (cig1, cig2, puc1, and cdc13 cyclins) and negative (rum1 and ste9-APC) regulators of cdc2. Early in G1, cyclin proteolysis a...

In fission yeast, the cyclin-dependent kinase (CDK) inhibitor p25(rum1) is a key regulator of progression through the G1 phase of the cell cycle. We show here that p25(rum1) protein levels are sharply periodic. p25(rum1) begins to accumulate at anaphase, persists in G1 and is destroyed during S phase. p25(rum1 )is stabilized and polyubiquitinated i...

In eukaryotes, cell division is controlled by cyclin-dependent kinases (CDKs). Here we summarize a few new developments on the regulation of the cell cycle by CDK-cyclin complexes. We have focused on three aspects in which there has been recent progress: the structural analysis of these complexes, the phenotypes of mice carrying knockouts of CDK in...

Recently it has been found that B-type cyclins in fission yeast regulate the activation of the cdc2 kinase to promote the onset of both DNA replication and mitosis. cig2 is the major G1 cyclin while cdc13 is the principal mitotic cyclin. cdc13 also has an additional function in G2 phase, preventing more than one round of DNA replication per cell cy...

The onset of S phase in fission yeast is regulated at Start, the point of commitment to the mitotic cell cycle. The p34cdc2 kinase is essential for G1 progression past Start, but until now its regulation has been poorly understood. Here we show that the cig2/cyc17 B-type cyclin has an important role in G1 progression, and demonstrate that p34cdc2 k...