USP37 prevents unscheduled replisome unloading through MCM complex deubiquitination.

The CMG helicase (CDC45-MCM2-7-GINS) unwinds DNA as a component of eukaryotic replisomes. Replisome (dis)assembly is tightly coordinated with cell cycle progression to ensure genome stability. However, factors that prevent premature CMG unloading and replisome disassembly are poorly described.

Endothelial Cell Flow-Mediated Quiescence Is Temporally Regulated and Utilizes the Cell Cycle Inhibitor p27.

Background: Endothelial cells regulate their cell cycle as blood vessels remodel and transition to quiescence downstream of blood flow-induced mechanotransduction. Laminar blood flow leads to quiescence, but how flow-mediated quiescence is established and maintained is poorly understood.

Methods: Primary human endothelial cells were exposed to laminar flow regimens and gene expression manipulations, and quiescence depth was analyzed via time-to-cell cycle reentry after flow cessation.

APC/C prevents non-canonical order of cyclin/CDK activity to maintain CDK4/6 inhibitor-induced arrest.

Regulated cell cycle progression ensures homeostasis and prevents cancer. In proliferating cells, premature S phase entry is avoided by the E3 ubiquitin ligase APC/C (anaphase promoting complex/cyclosome), although the APC/C substrates whose degradation restrains G1-S progression are not fully known. The APC/C is also active in arrested cells that exited the cell cycle, but it is not clear if APC/C maintains all types of arrest.

Non-canonical function of histone methyltransferase G9a in the translational regulation of chronic inflammation.

We report a novel translation-regulatory function of G9a, a histone methyltransferase and well-understood transcriptional repressor, in promoting hyperinflammation and lymphopenia; two hallmarks of endotoxin tolerance (ET)-associated chronic inflammatory complications. Using multiple approaches, we demonstrate that G9a interacts with multiple translation regulators during ET, particularly the N6-methyladenosine (mA) RNA methyltransferase METTL3, to co-upregulate expression of certain mA-modified mRNAs that encode immune-checkpoint and anti-inflammatory proteins. Mechanistically, G9a promotes mA methyltransferase activity of METTL3 at translational/post-translational level by regulating its expression, its methylation, and its cytosolic localization during ET.

G1 Dynamics at the Crossroads of Pluripotency and Cancer.

G1 cell cycle phase dynamics are regulated by intricate networks involving cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors, which control G1 progression and ensure proper cell cycle transitions. Moreover, adequate origin licensing in G1 phase, the first committed step of DNA replication in the subsequent S phase, is essential to maintain genome integrity. In this review, we highlight the intriguing parallels and disparities in G1 dynamics between stem cells and cancer cells, focusing on their regulatory mechanisms and functional outcomes.

Endothelial cell flow-mediated quiescence is temporally regulated and utilizes the cell cycle inhibitor p27.

Background: Endothelial cells regulate their cell cycle as blood vessels remodel and transition to quiescence downstream of blood flow-induced mechanotransduction. Laminar blood flow leads to quiescence, but how flow-mediated quiescence is established and maintained is poorly understood.

Methods: Primary human endothelial cells were exposed to laminar flow regimens and gene expression manipulations, and quiescence depth was analyzed via time to cell cycle re-entry after flow cessation.

Cell cycle exits and U-turns: Quiescence as multiple reversible forms of arrest.

Cell proliferation control is essential during development and for maintaining adult tissues. Loss of that control promotes not only oncogenesis when cells proliferate inappropriately but also developmental abnormalities or degeneration when cells fail to proliferate when and where needed. To ensure that cells are produced at the right place and time, an intricate balance of pro-proliferative and anti-proliferative signals impacts the probability that cells undergo cell cycle exit to quiescence, or G phase.

STING Suppresses Mitochondrial VDAC2 to Govern RCC Growth Independent of Innate Immunity.

STING is an innate immune sensor for immune surveillance of viral/bacterial infection and maintenance of an immune-friendly microenvironment to prevent tumorigenesis. However, if and how STING exerts innate immunity-independent function remains elusive. Here, the authors report that STING expression is increased in renal cell carcinoma (RCC) patients and governs tumor growth through non-canonical innate immune signaling involving mitochondrial ROS maintenance and calcium homeostasis.

The molecular architecture of cell cycle arrest.

The cellular decision governing the transition between proliferative and arrested states is crucial to the development and function of every tissue. While the molecular mechanisms that regulate the proliferative cell cycle are well established, we know comparatively little about what happens to cells as they diverge into cell cycle arrest. We performed hyperplexed imaging of 47 cell cycle effectors to obtain a map of the molecular architecture that governs cell cycle exit and progression into reversible ("quiescent") and irreversible ("senescent") arrest states.

Chromosomal localization of cohesin is differentially regulated by WIZ, WAPL, and G9a.

Background: The cohesin complex is essential for proper chromosome structure and gene expression. Defects in cohesin subunits and regulators cause changes in cohesin complex dynamics and thereby alter three-dimensional genome organization. However, the molecular mechanisms that drive cohesin localization and function remain poorly understood.

Quantitative profiling of adaptation to cyclin E overproduction.

Cyclin E/CDK2 drives cell cycle progression from G1 to S phase. Despite the toxicity of cyclin E overproduction in mammalian cells, the cyclin E gene is overexpressed in some cancers. To further understand how cells can tolerate high cyclin E, we characterized non-transformed epithelial cells subjected to chronic cyclin E overproduction.

The consequences of differential origin licensing dynamics in distinct chromatin environments.

Eukaryotic chromosomes contain regions of varying accessibility, yet DNA replication factors must access all regions. The first replication step is loading MCM complexes to license replication origins during the G1 cell cycle phase. It is not yet known how mammalian MCM complexes are adequately distributed to both accessible euchromatin regions and less accessible heterochromatin regions.

CDK4/6 inhibitors induce replication stress to cause long-term cell cycle withdrawal.

CDK4/6 inhibitors arrest the cell cycle in G1-phase. They are approved to treat breast cancer and are also undergoing clinical trials against a range of other tumour types. To facilitate these efforts, it is important to understand why a cytostatic arrest in G1 causes long-lasting effects on tumour growth.

Stress Relief Techniques: p38 MAPK Determines the Balance of Cell Cycle and Apoptosis Pathways.

Protein signaling networks are formed from diverse and inter-connected cell signaling pathways converging into webs of function and regulation. These signaling pathways both receive and conduct molecular messages, often by a series of post-translation modifications such as phosphorylation or through protein-protein interactions via intrinsic motifs. The mitogen activated protein kinases (MAPKs) are components of kinase cascades that transmit signals through phosphorylation.

Efficiency and equity in origin licensing to ensure complete DNA replication.

The cell division cycle must be strictly regulated during both development and adult maintenance, and efficient and well-controlled DNA replication is a key event in the cell cycle. DNA replication origins are prepared in G1 phase of the cell cycle in a process known as origin licensing which is essential for DNA replication initiation in the subsequent S phase. Appropriate origin licensing includes: (1) Licensing enough origins at adequate origin licensing speed to complete licensing before G1 phase ends; (2) Licensing origins such that they are well-distributed on all chromosomes.

Bi-allelic MCM10 variants associated with immune dysfunction and cardiomyopathy cause telomere shortening.

Minichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication. Here, we describe compound heterozygous MCM10 variants in patients with distinctive, but overlapping, clinical phenotypes: natural killer (NK) cell deficiency (NKD) and restrictive cardiomyopathy (RCM) with hypoplasia of the spleen and thymus. To understand the mechanism of MCM10-associated disease, we modeled these variants in human cell lines.

Novel gene-specific translation mechanism of dysregulated, chronic inflammation reveals promising, multifaceted COVID-19 therapeutics.

Hyperinflammation and lymphopenia provoked by SARS-CoV-2-activated macrophages contribute to the high mortality of Coronavirus Disease 2019 (COVID-19) patients. Thus, defining host pathways aberrantly activated in patient macrophages is critical for developing effective therapeutics. We discovered that G9a, a histone methyltransferase that is overexpressed in COVID-19 patients with high viral load, activates translation of specific genes that induce hyperinflammation and impairment of T cell function or lymphopenia.

Programming pluripotent stem cells: Can't teach an old cell new DNA replication tricks.

Pluripotent stem cells differentiate with varying efficiencies depending on the method of reprogramming that created them. In this issue, Paniza et al. (2020.

Distinct and sequential re-replication barriers ensure precise genome duplication.

Achieving complete and precise genome duplication requires that each genomic segment be replicated only once per cell division cycle. Protecting large eukaryotic genomes from re-replication requires an overlapping set of molecular mechanisms that prevent the first DNA replication step, the DNA loading of MCM helicase complexes to license replication origins, after S phase begins. Previous reports have defined many such origin licensing inhibition mechanisms, but the temporal relationships among them are not clear, particularly with respect to preventing re-replication in G2 and M phases.

SGC-AAK1-1: A Chemical Probe Targeting AAK1 and BMP2K.

Inhibitors based on a 3-acylaminoindazole scaffold were synthesized to yield potent dual AAK1/BMP2K inhibitors. Optimization furnished a small molecule chemical probe (SGC-AAK1-1, ) that is potent and selective for AAK1/BMP2K over other NAK family members, demonstrates narrow activity in a kinome-wide screen, and is functionally active in cells. This inhibitor represents one of the best available small molecule tools to study the functions of AAK1 and BMP2K.

Mass spectrometry-based selectivity profiling identifies a highly selective inhibitor of the kinase MELK that delays mitotic entry in cancer cells.

The maternal embryonic leucine zipper kinase (MELK) has been implicated in the regulation of cancer cell proliferation. RNAi-mediated MELK depletion impairs growth and causes G/M arrest in numerous cancers, but the mechanisms underlying these effects are poorly understood. Furthermore, the MELK inhibitor OTSSP167 has recently been shown to have poor selectivity for MELK, complicating the use of this inhibitor as a tool compound to investigate MELK function.

Preparation for DNA replication: the key to a successful S phase.

Successful genome duplication is required for cell proliferation and demands extraordinary precision and accuracy. The mechanisms by which cells enter, progress through, and exit S phase are intense areas of focus in the cell cycle and genome stability fields. Key molecular events in the G1 phase of the cell division cycle, especially origin licensing, are essential for pre-establishing conditions for efficient DNA replication during the subsequent S phase.