Biology subjects

Gutierrez-Escribano, P.

Publications and source records attributed to Gutierrez-Escribano, P..

5 recordsLinked to original sources

bioRxiv2026

Killer meiotic driver prevents chromosome loss and enhances fitness in a fungal pathogen

Fungal pathogens often carry dispensable chromosomes (DCs) that confer a selective advantage in adverse environments or during host infection but can be spontaneously lost under non-selective conditions. How DCs are maintained in evolving populations remains poorly understood. Here we show that a meiotic driver known as Spore Killer (spok), located on a giant Starship transposon, limits spontaneous loss of a conserved DC in the cross-kingdom pathogen Fusarium oxysporum. Transfer of a functional spok gene, but not of a killing-deficient mutant allele, to a mitotically unstable DC significantly reduced its loss rate, while spok deletion from a stably maintained DC increased loss frequency. Competition experiments between isogenic strains carrying a functional or a killing-deficient spok allele revealed a dramatic fitness gain conferred by Spok killing activity, which required transmission by hyphal fusion. Thus, spoks and their Starship carriers benefit fungal hosts by preventing DC loss and preserving long-term metabolic and pathogenic plasticity.

microbiology↗

bioRxiv2022

Condensin pinches a short negatively supercoiledDNA loop during each round of ATP usage

Condensin extrudes DNA loops using an ATP-dependent mechanism that remains to be elucidated. Here, we show how condensin activity alters the topology of the interacting DNA. High condensin concentrations restrain DNA positive supercoils. However, in experimental conditions that sustain DNA loop extrusion, condensin restrains negative supercoils. Namely, upon ATP-mediated loading onto DNA, each condensin constrains a DNA linking number difference ({Delta}Lk) of -0.4. This {Delta}Lk increases to -0.8 during ATP binding and resets to -0.4 upon ATP hydrolysis. These {Delta}Lk values reflect the transient formation of a short left-handed loop of DNA, which is not the extruding loop. We conclude that, upon condensin ATPase-head engagement, a segment of DNA is pinched to form a short negatively supercoiled loop, which can be subsequently merged with the extruding loop. Such "pinch and merge" mechanism implies that the DNA is transferred between two dynamic DNA-binding sites while anchored at a third site.

molecular biology↗

bioRxiv2019

FACT mediates cohesin function on chromatin

Cohesin is a key regulator of genome architecture with roles in sister chromatid cohesion 1,2 and the organisation of higher-order structures during interphase 3 and mitosis 4,5. The recruitment and mobility of cohesin complexes on DNA is restricted by nucleosomes 6-8. Here we show that cohesin role in chromosome organisation requires the histone chaperone FACT. Depletion of FACT in metaphase cells affects cohesin stability on chromatin reducing its accumulation at pericentric regions and binding on chromosome arms. Using Hi-C, we show that cohesin-dependent TAD (Topological Associated Domains)-like structures in G1 and metaphase chromosomes are disrupted in the absence of FACT. Surprisingly, sister chromatid cohesion is intact in FACT-depleted cells, although chromosome segregation failure is observed. Our results uncover a role for FACT in genome organisation by facilitating cohesin-dependent compartmentalization of chromosomes into loop domains.

molecular biology↗

bioRxiv2019

A conserved activity for cohesin in bridging DNA molecules

Essential processes such as accurate chromosome segregation, regulation of gene expression and DNA repair rely on protein-mediated DNA tethering. Sister chromatid cohesion requires the SMC complex cohesin to act as a protein linker that holds replicated chromatids together (1, 2). The molecular mechanism by which cohesins hold sister chromatids has remained controversial. Here, we used a single molecule approach to visualise the activity of cohesin complexes as they hold DNA molecules. We describe a DNA bridging activity that requires ATP and is conserved from yeast to human cohesin. We show that cohesin can form two distinct classes of bridges at physiological conditions, a \"permanent bridge\" able to resists high force (over 80pN) and a \"reversible bridge\" that breaks at lower forces (5-40pN). Both classes of bridges require Scc2/Scc4 in addition to ATP. We demonstrate that bridge formation requires physical proximity of the DNA segments to be tethered and show that \"permanent\" cohesin bridges can move between two DNA molecules but cannot be removed from DNA when they occur in cis. This suggests that separate physical compartments in cohesin molecules are involved in the bridge. Finally, we show that cohesin tetramers, unlike condensin, cannot compact linear DNA molecules against low force, demonstrating that the core activity of cohesin tetramers is bridging DNA rather than compacting it. Our findings carry important implications for the understanding of the basic mechanisms behind cohesin-dependent establishment of sister chromatid cohesion and chromosome architecture.

biochemistry↗

bioRxiv2018

PP4 phosphatase cooperates in recombinational DNA repair by enhancing double-strand break end resection

The role of Rad53 in response to a DNA lesion is central for the accurate orchestration of the DNA damage response. Rad53 activation relies on its phosphorylation by the Mec1 kinase and its own auto-phosphorylation in a manner dependent on the adaptor Rad9. While the mechanism behind Rad53 phosphorylation and activation has been well documented, less is known about the processes that counteract its kinase activity during the response to DNA damage. Here, we describe that PP4 phosphatase dephosphorylates Rad53 during the repair of a double-strand break, a process that impacts on the phosphorylation status of multiple factors involved in the DNA damage response. PP4-dependent Rad53 dephosphorylation stimulates DNA end resection by relieving the negative effect that Rad9 exerts over the Sgs1/Dna2 exonuclease complex. Consequently, elimination of PP4 activity affects DNA resection and repair by single-strand annealing, defects that are bypassed by reducing the hyper-phosphorylation state of Rad53 observed in the absence of the phosphatase. These results confirm that Rad53 is one of the main targets of PP4 during the repair of a DNA lesion and demonstrate that the attenuation of its kinase activity during the initial steps of the repair process is essential to efficiently enhance recombinational DNA repair pathways that depend on long-range resection.

molecular biology↗