Maikel Castellano-Pozo

Genomic stability maintenance requires the repair of DNA breaks in the most accurate fashion. So, an exquisite regulatory network controls the choice between different repair mechanisms to maximize genome integrity. This relies mostly at the level of DNA end resection, the initial steps of the homologous recombination. On the other hand, numerous cellular activities follow a 24 h oscillation known as the circadian cycle. Thus, we explored the regulation of the choice between different DNA break repair pathways along the circadian cycle. Here we show that in human cells DNA resection shows a circadian oscillation, with a peak at early morning followed by a partial and progressive reduction until late afternoon. Such regulation depends on the circadian clock core component CRY1, which modulates the anti-resection activity of CCAR2 to limit CtIP at nightfall. Additionally, such regulation requires DNA-PK-mediated phosphorylation of CRY1. Finally, this circadian regulation impacts cancer progression and response to radiation therapy of specific tumours.

We synthesised coumarin-based derivatives bearing thio- and selenocyanates to selectively inhibit tumour-associated carbonic anhydrases (CAs) IX and XII and to exert antiproliferative effects on tumour cells. Structural variations included chalcogen atom type (S, Se), substitutions at C-3/C-4, and tether length at C-7 of the coumarin core. Thiocyanates 4 and 7b showed potent CA IX/XII inhibition (K_i = 17.9-27.4 nM) with >5000-fold selectivity over off-target isoforms (CAs I and II). Selenocyanate 8a exhibited strong antiproliferative activity (GI₅₀ = 0.78-2.6 µM) across six human solid tumour cell lines. Mechanistic studies revealed a cytostatic effect via cell cycle arrest and reduced mitotic progression. In vivo assays in Caenorhabditis elegans confirmed selective cytostatic action of selenocyanate 8c, reducing tumorous germline size without affecting healthy tissues at therapeutic doses.

Advances in sequencing techniques have revealed extreme chromosomal diversity and underscored the importance of chromoanagenesis in macroevolution, speciation, and the context of cancer and tumor progression. Evolution is essential for adapting to the environment, preparing for future pressures, ensuring survival, and generating diversity. Here, we discuss some events like chromothripsis and other chromosomal rearrangements, emphasizing their roles as driving forces in genomic evolution from cancer to speciation.

Advances in sequencing techniques have revealed extreme chromosomal diversity andunderscored the importance of chromoanagenesis in macroevolution, speciation, and the contextof cancer and tumor progression. Evolution is essential for adapting to the environment, preparingfor future pressures, ensuring survival, and generating diversity. Here we discuss some events likechromothripsis and other chromosomal rearrangements, emphasizing their roles as driving forcesin genomic evolution from cancer to speciation.

En la educación universitaria es fundamental incorporar métodos que impulsen habilidades cruciales para el desarrollo académico y profesional de los estudiantes. A menudo, las prácticas convencionales en laboratorios siguen un enfoque estándar, donde se presenta un concepto teórico y a continuación se sigue un protocolo preestablecido sin estimular el pensamiento crítico del estudiante. Con la intención de solventar esta carencia, en este capítulo se describe el diseño y la aplicación de un ciclo de mejora docente en las prácticas de la asignatura Genética I, del Grado en Biología. Este ciclo de mejora se basa, principalmente, en la aplicación de la metodología del aula invertida, con el objetivo de fomentar una mayor adquisición de conocimientos y habilidades prácticas a través del razonamiento crítico durante todo el proceso de enseñanza. La aplicación de esta nueva metodología en las prácticas de laboratorio ha generado un mayor interés y motivación entre los estudiantes, evidenciándose en una mayor participación, mejor asimilación y comprensión de los contenidos. La satisfacción de los alumnos con este enfoque refleja el éxito de su implementación.

The cohesin complex plays essential roles in chromosome segregation, 3D genome organisation, and DNA damage repair through its ability to modify DNA topology. In higher eukaryotes, meiotic chromosome function, and therefore fertility, requires cohesin complexes containing meiosis-specific kleisin subunits: REC8 and RAD21L in mammals and REC-8 and COH-3/4 in Caenorhabditis elegans. How these complexes perform the multiple functions of cohesin during meiosis and whether this involves different modes of DNA binding or dynamic association with chromosomes is poorly understood. Combining time-resolved methods of protein removal with live imaging and exploiting the temporospatial organisation of the C. elegans germline, we show that REC-8 complexes provide sister chromatid cohesion (SCC) and DNA repair, while COH-3/4 complexes control higher-order chromosome structure. High-abundance COH-3/4 complexes associate dynamically with individual chromatids in a manner dependent on cohesin loading (SCC-2) and removal (WAPL-1) factors. In contrast, low-abundance REC-8 complexes associate stably with chromosomes, tethering sister chromatids from S-phase until the meiotic divisions. Our results reveal that kleisin identity determines the function of meiotic cohesin by controlling the mode and regulation of cohesin–DNA association, and are consistent with a model in which SCC and DNA looping are performed by variant cohesin complexes that coexist on chromosomes.

The integrity of the genome is crucial for the survival of all living organisms. However, genomes need to adapt to survive certain pressures, and for this purpose use several mechanisms to diversify. Chromosomal instability (CIN) is one of the main mechanisms leading to the creation of genomic heterogeneity by altering the number of chromosomes and changing their structures. In this review, we will discuss the different chromosomal patterns and changes observed in speciation, in evolutional biology as well as during tumor progression. By nature, the human genome shows an induction of diversity during gametogenesis but as well during tumorigenesis that can conclude in drastic changes such as the whole genome doubling to more discrete changes as the complex chromosomal rearrangement chromothripsis. More importantly, changes observed during speciation are strikingly similar to the genomic evolution observed during tumor progression and resistance to therapy. The different origins of CIN will be treated as the importance of double-strand breaks (DSBs) or the consequences of micronuclei. We will also explain the mechanisms behind the controlled DSBs, and recombination of homologous chromosomes observed during meiosis, to explain how errors lead to similar patterns observed during tumorigenesis. Then, we will also list several diseases associated with CIN, resulting in fertility issues, miscarriage, rare genetic diseases, and cancer. Understanding better chromosomal instability as a whole is primordial for the understanding of mechanisms leading to tumor progression.

The integrity of the genome is crucial for the survival of all living organisms. However, genomes need to adapt to survive certain pressures and for this propose use several mechanisms to diversify. Chromosomal instability (CIN) is one of the main mechanism leading to the creation of genomic heterogeneity by altering the number of chromosomes as well as changing their structures. In this review we will discuss the different chromosomal patterns and changes observed in speciation, in evolutional biology as well as during tumor progression. By nature, human genome shows induction of diversity during gametogenesis but as well during tumorigenesis that can conclude in drastic changes such as whole genome doubling to more discrete changes as indels as well as the recent discovered complex chromosomal rearrangement chromothripsis. More importantly, changes observed during speciation are strikingly similar to the genomic evolution observed during tumor progression and resistance to therapy. The different origins of CIN will be treated as the importance of double strand breaks (DSB) or the consequences of micronuclei. We will also explain the mechanisms behind the controlled DSBs and recombination of homologous chromosomes observed during meiosis, to explain how errors lead to similar pattern observed during tumorigenesis. Then, we will also list several diseases associated to CIN resulting in fertility issue, miscarriage, genetic rare diseases and cancer. Understanding better chromosomal instability as a whole is primordial for the understanding of mechanisms leading to tumor progression.

The maintenance of genomic stability is essential for cellular and organismal survival and fitness. Thus, when DNA gets damaged, is essential to repair it in the most accurate fashion. Among different DNA lesions, DNA double strand breaks are specially challenging. An exquisite regulatory network reacts to local and global cues to control the choice between different DNA double strand break repair mechanisms to maximize genomic integrity. Such regulation relies mostly at the level of DNA end resection, the initial steps of the homologous recombination repair pathway. On the other hand, most cellular and organismal activities follow a 24 h oscillation known as the circadian cycle. Such repetitive changes are controlled by an intrinsic, molecular clock built-in at the cellular level which core components are the heterodimers BMAL1-CLOCK and CRY-PER. These inherent rhythms control many different aspects of the cellular metabolism, including the fate of many different DNA transactions. Here we have explored the regulation of the choice between different DNA double strand break repair pathways along the circadian cycle. We observed that DNA end resection shows a circadian oscillation, with a peak at dawn followed by a progressive reduction until dusk. Such regulations depend on the cellular levels of the circadian clock core component CRY1. Consequently, repair by homologous recombination mirrors CRY1 expression levels. Such modulation is controlled through the circadian regulation of the anti-resection activity, but not the protein levels, of CCAR2, that limits CtIP-mediated resection preferentially at nightfall. Additionally, such regulation requires a crosstalk between the DNA damage-dependent phosphorylation of CRY1 by the kinase DNA-PK. Finally, such regulation has an impact in cancer progression and response to radiation therapy of specific tumors. One sentence summary CCAR2-dependent inhibition of DNA end resection and homologous recombination is controlled by the intrinsic cellular circadian clock