Optimized biochemical method for human Polyphosphate quantification.

Polyphosphate (polyP), a biopolymer composed of phosphates, impacts a wide range of biological functions and pathological conditions in all organisms. However, polyP's intricate physiology and structure in human cells have remained elusive, largely due to the lack of a reliable quantification method including its extraction. In this study, we assess critical points in the whole process: extraction, purification, and quantification polyP from human cell lines.

CDK6 is activated by the atypical cyclin I to promote E2F-mediated gene expression and cancer cell proliferation.

Cyclin-dependent kinases (CDKs), together with their cyclin partners, are the master cell cycle regulators. Remarkably, the cyclin family was extended to include atypical cyclins, characterized by distinctive structural features, but their partner CDKs remain elusive. Here, we conducted a yeast two-hybrid screen to identify new atypical cyclin-CDK complexes.

Association between soluble angiotensin-converting enzyme 2 in saliva and SARS-CoV-2 infection: a cross-sectional study.

This study aimed to investigate the association between saliva soluble angiotensin-converting enzyme 2 (sACE2) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children and adults. We selected a convenience sample of adults with post-acute SARS-CoV-2 infection and their household children living in quarantined family households of the metropolitan Barcelona region (Spain) during the spring 2020 pandemic national lockdown. Participants were tested for saliva sACE2 quantification by western blot and nasopharyngeal SARS-CoV-2 RT-PCR detection.

Determination of soluble angiotensin-converting enzyme 2 in saliva samples and its association with nicotine.

Introduction: The Angiotensin-Converting Enzyme 2 (ACE2) is the main receptor of the SARS-CoV-2. There is contradictory evidence on how the exposure to nicotine may module the concentration of soluble ACE2 (sACE2). The aim of this study was to assess the association between nicotine and sACE2 concentrations in saliva samples.

Protocol to quantify polyphosphate in human cell lines using a tagged PPBD peptide.

Polyphosphate (polyP) is an evolutionarily conserved polymer of phosphates that is difficult to study in human cells because of its low concentration and high lability. First, we described how to express and purify Xpress-tagged PPBD (Ppx1 PolyP Binding Domain). We describe the detection and quantification of nuclear polyP in HEK293T cells using Xpress-PPBD, Xpress antibody, and Alexa-conjugated secondary antibodies.

Mad3 modulates the G Cdk and acts as a timer in the Start network.

Cells maintain their size within limits over successive generations to maximize fitness and survival. Sizer, timer, and adder behaviors have been proposed as possible alternatives to coordinate growth and cell cycle progression. Regarding budding yeast cells, a sizer mechanism is thought to rule cell cycle entry at Start.

Polyphosphate degradation by Nudt3-Zn mediates oxidative stress response.

Polyphosphate (polyP) is a polymer of hundreds of phosphate residues present in all organisms. In mammals, polyP is involved in crucial physiological processes, including coagulation, inflammation, and stress response. However, after decades of research, the metabolic enzymes are still unknown.

Atypical cyclin P regulates cancer cell stemness through activation of the WNT pathway.

Purpose: Cancer stem cells represent a cancer cell subpopulation that has been found to be associated with metastasis and chemoresistance. Therefore, it is vital to identify mechanisms regulating cancer stemness. Previously, we have shown that the atypical cyclin P (CCNP), also known as CNTD2, is upregulated in lung and colorectal cancers and is associated with a worse clinical prognosis.

CDK-mediated Yku80 Phosphorylation Regulates the Balance Between Non-homologous End Joining (NHEJ) and Homologous Directed Recombination (HDR).

There are two major pathways for repairing DNA double-strand breaks (DSBs): homologous directed recombination (HDR) and non-homologous end-joining (NHEJ). While NHEJ functions throughout the cell cycle, HDR is only possible during S/G phases, suggesting that there are cell cycle-specific mechanisms regulating the balance between the two repair systems. The regulation exerted by CDKs on HDR has been extensively demonstrated, and here we present evidence that the CDK Pho85, in association with the G cyclin Pcl1, phosphorylates Yku80 on Ser 623 to regulate NHEJ activity.

Atypical cyclins in cancer: New kids on the block?

Atypical cyclins have recently emerged as a new subfamily of cyclins characterized by common structural features and interactor pattern. Interestingly, atypical cyclins are phylogenetically close to canonical cyclins, which have well-established roles in cell cycle regulation and cancer. Therefore, although the function of atypical cyclins is still poorly characterized, it seems likely that they are involved in cancer pathogenesis as well.

Atypical cyclins: the extended family portrait.

Regulation of cell division is orchestrated by cyclins, which bind and activate their catalytic workmates, the cyclin-dependent kinases (CDKs). Cyclins have been traditionally defined by an oscillating (cyclic) pattern of expression and by the presence of a characteristic "cyclin box" that determines binding to the CDKs. Noteworthy, the Human Genome Sequence Project unveiled the existence of several other proteins containing the "cyclin box" domain.

Comprehensive and quantitative analysis of G1 cyclins. A tool for studying the cell cycle.

In eukaryotes, the cell cycle is driven by the actions of several cyclin dependent kinases (CDKs) and an array of regulatory proteins called cyclins, due to the cyclical expression patterns of the latter. In yeast, the accepted pattern of cyclin waves is based on qualitative studies performed by different laboratories using different strain backgrounds, different growing conditions and media, and different kinds of genetic manipulation. Additionally, only the subset of cyclins regulating Cdc28 was included, while the Pho85 cyclins were excluded.

Phosphoregulation of the oncogenic protein regulator of cytokinesis 1 (PRC1) by the atypical CDK16/CCNY complex.

CDK16 (also known as PCTAIRE1 or PCTK1) is an atypical member of the cyclin-dependent kinase (CDK) family that forms an active complex with cyclin Y (CCNY). Although both proteins have been recently implicated in cancer pathogenesis, it is still unclear how the CDK16/CCNY complex exerts its biological activity. To understand the CDK16/CCNY network, we used complementary proteomic approaches to identify potential substrates of this complex.

The atypical cyclin CNTD2 promotes colon cancer cell proliferation and migration.

Colorectal cancer (CRC) is one of the most common cancers worldwide, with 8-10% of these tumours presenting a BRAF (V600E) mutation. Cyclins are known oncogenes deregulated in many cancers, but the role of the new subfamily of atypical cyclins remains elusive. Here we have performed a systematic analysis of the protein expression levels of eight atypical cyclins in human CRC tumours and several cell lines, and found that CNTD2 is significantly upregulated in CRC tissue compared to the adjacent normal one.

Centromeric signaling proteins boost G1 cyclin degradation and modulate cell size in budding yeast.

Cell size scales with ploidy in a great range of eukaryotes, but the underlying mechanisms remain unknown. Using various orthogonal single-cell approaches, we show that cell size increases linearly with centromere (CEN) copy number in budding yeast. This effect is due to a G1 delay mediated by increased degradation of Cln3, the most upstream G1 cyclin acting at Start, and specific centromeric signaling proteins, namely Mad3 and Bub3.

Intertwined control of the cell cycle and nucleocytoplasmic transport by the cyclin-dependent kinase Pho85 and RanGTPase Gsp1 in Saccharomyces cerevisiae.

Deciphering the molecular mechanisms that connect cell cycle progression and nucleocytoplasmic transport is of particular interest: this intertwined relationship, once understood, may provide useful insight on the diseases resulting from the malfunction of these processes. In the present study we report on findings that indicate a biochemical connection between the cell cycle regulator CDK Pho85 and Ran-GTPase Gsp1, an essential nucleocytoplasmic transport component. When Gsp1 cannot be phosphorylated by Pho85, the cell cycle progression is impaired.

Polyphosphate is a key factor for cell survival after DNA damage in eukaryotic cells.

Cells require extra amounts of dNTPs to repair DNA after damage. Polyphosphate (polyP) is an evolutionary conserved linear polymer of up to several hundred inorganic phosphate (Pi) residues that is involved in many functions, including Pi storage. In the present article, we report on findings demonstrating that polyP functions as a source of Pi when required to sustain the dNTP increment essential for DNA repair after damage.

Phosphate: from stardust to eukaryotic cell cycle control.

Phosphorus is a pivotal element in all biochemical systems: it serves to store metabolic energy as ATP, it forms the backbone of genetic material such as RNA and DNA, and it separates cells from the environment as phospholipids. In addition to this "big hits", phosphorus has recently been shown to play an important role in other important processes such as cell cycle regulation. In the present review, we briefly summarize the biological processes in which phosphorus is involved in the yeast Saccharomyces cerevisiae before discussing our latest findings on the role of this element in the regulation of DNA replication in this eukaryotic model organism.

Improvement of biochemical methods of polyP quantification.

Polyphosphate (polyP) is an abundant and physiologically important biomolecule for virtually any living cell. Therefore, determination of changes in cellular content of polyP is crucial for its functional characterization. Determination of cellular polyP has been performed by many different methods, and the lack of a standardized procedure is possibly responsible for the large dispersion of results found in the relevant literature.

Polyphosphate: popping up from oblivion.

Phosphate is one of the essential elements supporting life. Cells accumulate phosphate in the form of a molecule called polyphosphate (polyP), which carries many functions in the physiology of cells that have not been wholly elucidated. Polyphosphate is present in all the types of cells from bacteria to mammals.

Polyphosphate is involved in cell cycle progression and genomic stability in Saccharomyces cerevisiae.

Polyphosphate (polyP) is a linear chain of up to hundreds of inorganic phosphate residues that is necessary for many physiological functions in all living organisms. In some bacteria, polyP supplies material to molecules such as DNA, thus playing an important role in biosynthetic processes in prokaryotes. In the present study, we set out to gain further insight into the role of polyP in eukaryotic cells.

The quantitative changes in the yeast Hsp70 and Hsp90 interactomes upon DNA damage.

The molecular chaperones Hsp70 and Hsp90 participate in many important cellular processes, including how cells respond to DNA damage. Here we show the results of applied quantitative affinity-purification mass spectrometry (AP-MS) proteomics to understand the protein network through which Hsp70 and Hsp90 exert their effects on the DNA damage response (DDR). We characterized the interactomes of the yeast Hsp70 isoform Ssa1 and Hsp90 isoform Hsp82 before and after exposure to methyl methanesulfonate.

Hog1 targets Whi5 and Msa1 transcription factors to downregulate cyclin expression upon stress.

Yeast cells have developed complex mechanisms to cope with extracellular insults. An increase in external osmolarity leads to activation of the stress-activated protein kinase Hog1, which is the main regulator of adaptive responses, such as gene expression and cell cycle progression, that are essential for cellular survival. Upon osmostress, the G1-to-S transition is regulated by Hog1 through stabilization of the cyclin-dependent kinase inhibitor Sic1 and the downregulation of G1 cyclin expression by an unclear mechanism.

Live fast, die soon: cell cycle progression and lifespan in yeast cells.

Our understanding of lifespan has benefited enormously from the study of a simple model, the yeast . Although a unicellular organism, yeasts undergo many of the processes directly related with aging that to some extent are conserved in mammalian cells. Nutrient-limiting conditions have been involved in lifespan extension, especially in the case of caloric restriction, which also has a direct impact on cell cycle progression.