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Papers by Victor Bolanos-garcia

Frontiers in Physiology, Sep 27, 2022

Elsevier eBooks, 2014

Specific interactions within the cell must occur in a crowded environment and often in a narrow t... more Specific interactions within the cell must occur in a crowded environment and often in a narrow time-space framework to ensure cell survival. In the light that up to 10% of individual protein molecules present at one time in mammalian cells mediate signal transduction, the establishment of productive, specific interactions is a remarkable achievement. The spindle assembly checkpoint (SAC) is an evolutionarily conserved and essential self-monitoring system of the eukaryotic cell cycle that ensures the high fidelity of chromosome segregation by delaying the onset of anaphase until all chromosomes are properly bi-oriented on the mitotic spindle. The function of the SAC involves communication with the kinetochore, an essential multiprotein complex crucial for chromosome segregation that assembles on mitotic or meiotic centromeres to link centromeric DNA with microtubules. Interactions in the SAC and kinetochore-microtubule network often involve the reversible assembly of large multiprotein complexes in which regions of the polypeptide chain that exhibit low structure complexity undergo a disorder-to-order transition. The confinement and high density of protein molecules in the cell has a profound effect on the stability, folding rate, and biological functions of individual proteins and protein assemblies. Here, I discuss the role of large and highly flexible surfaces that mediate productive intermolecular interactions in SAC signaling and postulate that macromolecular crowding contributes to the exquisite regulation that is required for the timely and accurate segregation of chromosomes in higher organisms.

Methods in molecular biology, 2024

Subcellular Biochemistry, 2017

Mistakes in the process of cell division can lead to the loss, gain or rearrangement of chromosom... more Mistakes in the process of cell division can lead to the loss, gain or rearrangement of chromosomes. Significant chromosomal abnormalities are usually lethal to the cells and cause spontaneous miscarriages. However, in some cases, defects in the spindle assembly checkpoint lead to severe diseases, such as cancer and birth and development defects, including Down's syndrome. The timely and accurate control of chromosome segregation in mitosis relies on the spindle assembly checkpoint (SAC), an evolutionary conserved, self-regulated signalling system present in higher organisms. The spindle assembly checkpoint is orchestrated by dynamic interactions between spindle microtubules and the kinetochore , a multiprotein complex that constitutes the site for attachment of chromosomes to microtubule polymers to pull sister chromatids apart during cell division. This chapter discusses the current molecular understanding of the essential, highly dynamic molecular interactions underpinning spindle assembly checkpoint signalling and how the complex choreography of interactions can be coordinated in time and space to finely regulate the process. The potential of targeting this signalling pathway to interfere with the abnormal segregation of chromosomes, which occurs in diverse malignancies and the new opportunities that recent technological developments are opening up for a deeper understanding of the spindle assembly checkpoint are also discussed.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 12, 2012

HAL (Le Centre pour la Communication Scientifique Directe), 2016

International audienceLipoprotein(a) [Lp(a)] was identified in 1963 in human serum as an LDL-like... more International audienceLipoprotein(a) [Lp(a)] was identified in 1963 in human serum as an LDL-like particle and is today recognized as an important risk factor for cardiovascular diseases (Ref: Nordestgaard and col. Lipoprotein(a) as a Cardiovascular Risk Factor: Current Status. Eur Heart J 2010; 31, 2844-53). The LDL-like core of Lp(a) is covalently bound to a unique plasminogen-related glycoprotein, called apolipoprotein(a) [apo(a)]. This protein is highly polymorphic between individuals due to a specific domain namely Kringle IV type2 (KIV-2), which can be present as tandemly repeated from 3 to >40 times. Apo(a) seems to be also responsible of many of the pro-atherogenic and pro-trombotic properties of Lp(a). For example, smaller apo(a) isoforms (i.e. Lp(a) isoforms with a low number of KIV-2 copies) correlate with higher cardiovascular risk (Ref: Gazzaruso C, et al. Association of lipoprotein(a) levels and apolipoprotein(a) phenotypes with coronary heart disease in patients with essential hypertension. J Hypertens 1997;15(3):227-35). However, the molecular basis underlying the different atherogenic potential has not been fully understood. Biophysical characterization of different Lp(a) isoforms may offer insights into the role of apo(a) size in atherosclerotic diseases. In this work, we present interfacial measurements of four purified Lp(a) isoforms containing 20, 24, 25 and 29 KIV-2 domains (K20, K24, K25, and K29)

HAL (Le Centre pour la Communication Scientifique Directe), Nov 1, 2021

Lipoprotein (a) [Lp(a)] is an LDL-like particle constituted by lipids, apolipoprotein B100 and ap... more Lipoprotein (a) [Lp(a)] is an LDL-like particle constituted by lipids, apolipoprotein B100 and apolipoprotein (a) [apo(a)], a multidomain glycoprotein whose molecular mass is dependent on the genetically encoded number of Kringle IV type 2 (KIV-2) repeats. Because Lp(a) isoforms have been associated with cardiovascular risk (CVR), we have investigated if their interfacial properties can contribute to distinguish between low and high-risk groups and thus be used as a new CVR indicator. Four Lp(a) variants, each carrying a different apo(a) isoform (K20, K24, K25, and K29), were purified from plasma of homozygous donors and their interfacial properties characterized using ellipsometry and surface pressure techniques. Ellipsometry measurements revealed that these isoforms had a similar propensity to form adsorbed layers at hydrophobic-hydrophilic interfaces, but surface pressure enabled to clearly separate them into two groups: K20 and K24 on one side, and K25 and K29 on the other side. Though K24 and K25 differ only by a single KIV-2 domain, their sharp difference in surface pressure suggests a critical threshold between the two Lp(a) forms, providing insights into the use of condensed matter approaches to monitor CVR. Our findings may represent a new laboratory window to assist medical decisions and to develop precision medicine treatments, practices, and products for CVR, which can be extended to other cardiovascular disease conditions.

Current Biology, 2011

Centromeres provide a region of chromatin upon which kinetochores are assembled in mitosis [1, 2]... more Centromeres provide a region of chromatin upon which kinetochores are assembled in mitosis [1, 2]. Centromeric protein C (CENP-C) is a core component of this centromeric chromatin [3, 4] that, when depleted, prevents the proper formation of both centromeres and kinetochores [5-10]. CENP-C localizes to centromeres throughout the cell cycle via its C-terminal part [6, 8], whereas its N-terminal part appears necessary for recruitment of some but not all components of the Mis12 complex of the kinetochore [8]. We now find that all kinetochore proteins belonging to the KMN (KNL1/Spc105, the Mis12 complex, and the Ndc80 complex) network [1] bind to the N-terminal part of Drosophila CENP-C. Moreover, we show that the Mis12 complex component Nnf1 interacts directly with CENP-C in vitro. To test whether CENP-C's N-terminal part was sufficient to recruit KMN proteins, we targeted it to the centrosome by fusing it to a domain of Plk4 kinase [11]. The Mis12 and Ndc80 complexes and Spc105 protein were then all recruited to centrosomes at the expense of centromeres, leading to mitotic abnormalities typical of cells with defective kinetochores. Thus, the N-terminal part of Drosophila CENP-C is sufficient to recruit core kinetochore components and acts as the principal linkage between centromere and kinetochore during mitosis. Results and Discussion Centromeres are patches of chromatin defined by the presence of the specific histone H3 variant called centromeric protein A (CENP-A)/CenH3 [12], also known as CID in Drosophila, Cse4 in S. cerevisiae, and Cnp1 in S. pombe (reviewed in [13]). Shortly before each mitosis, kinetochores are assembled on centromeres in a process whose mechanism and regulation are largely unknown. Recently published studies have pointed toward the centromeric protein CENP-C as a potential candidate for the regulatory role in kinetochore formation [7, 8]. CENP-C is localized at the centromeric chromatin throughout the cell cycle [4, 6]. It is embedded in the centromeric chromatin and, together with CENP-A, forms part of the core of the centromere. The carboxy-terminal part of CENP-C is known to be responsible

Frontiers in Physiology, Jul 25, 2022

The Anaphase Promoting Complex (APC/C), a large cullin-RING E3-type ubiquitin ligase, constitutes... more The Anaphase Promoting Complex (APC/C), a large cullin-RING E3-type ubiquitin ligase, constitutes the ultimate target of the Spindle Assembly Checkpoint (SAC), an intricate regulatory circuit that ensures the high fidelity of chromosome segregation in eukaryotic organisms by delaying the onset of anaphase until each chromosome is properly bi-oriented on the mitotic spindle. Cell-division cycle protein 20 homologue (CDC20) is a key regulator of APC/C function in mitosis. The formation of the APC/C CDC20 complex is required for the ubiquitination and degradation of select substrates, which is necessary to maintain the mitotic state. In contrast to the roles of CDC20 in animal species, little is known about CDC20 roles in the regulation of chromosome segregation in plants. Here we address this gap in knowledge and report the expression in insect cells; the biochemical and biophysical characterisation of Arabidopsis thaliana (AtCDC20) WD40 domain; and the nuclear and cytoplasmic distribution of full-length AtCDC20 when transiently expressed in tobacco plants. We also show that most AtCDC20 degrons share a high sequence similarity to other eukaryotes, arguing in favour of conserved degron functions in AtCDC20. However, important exceptions were noted such as the lack of a canonical MAD1 binding motif; a fully conserved RRY-box in all six AtCDC20 isoforms instead of a CRY-box motif, and low conservation of key residues known to be phosphorylated by BUB1 and PLK1 in other species to ensure a robust SAC response. Taken together, our studies provide insights into AtCDC20 structure and function and the evolution of SAC signalling in plants.