DREAM On: Cell Cycle Control in Development and Disease.

Perfectly orchestrated periodic gene expression during cell cycle progression is essential for maintaining genome integrity and ensuring that cell proliferation can be stopped by environmental signals. Genetic and proteomic studies during the past two decades revealed remarkable evolutionary conservation of the key mechanisms that control cell cycle-regulated gene expression, including multisubunit DNA-binding DREAM complexes. DREAM complexes containing a retinoblastoma family member, an E2F transcription factor and its dimerization partner, and five proteins related to products of Caenorhabditis elegans multivulva (Muv) class B genes lin-9, lin-37, lin-52, lin-53, and lin-54 (comprising the MuvB core) have been described in diverse organisms, from worms to humans. This review summarizes the current knowledge of the structure, function, and regulation of DREAM complexes in different organisms, as well as the role of DREAM in human disease.

Physiological effects of ivabradine in heart failure and beyond.

Ivabradine is a pharmacologic agent that inhibits the funny current responsible for determining heart rate in the sinoatrial node. Ivabradine's clinical potential has been investigated in the context of heart failure since it is associated with reduced myocardial oxygen demand, enhanced diastolic filling, stroke volume, and coronary perfusion time; however, it is yet to demonstrate definitive mortality benefit. Alternative effects of ivabradine include modulation of the renin-angiotensin-aldosterone system, sympathetic activation, and endothelial function. Here, we review key clinical trials informing the clinical use of ivabradine and explore opportunities for leveraging its potential pleiotropic effects in other diseases, including treatment of hyperadrenergic states and mitigating complications of COVID-19 infection.

Structural mechanism of Myb-MuvB assembly.

The MuvB transcriptional regulatory complex, which controls cell-cycle-dependent gene expression, cooperates with B-Myb to activate genes required for the G2 and M phases of the cell cycle. We have identified the domain in B-Myb that is essential for the assembly of the Myb-MuvB (MMB) complex. We determined a crystal structure that reveals how this B-Myb domain binds MuvB through the adaptor protein LIN52 and the scaffold protein LIN9. The structure and biochemical analysis provide an understanding of how oncogenic B-Myb is recruited to regulate genes required for cell-cycle progression, and the MMB interface presents a potential therapeutic target to inhibit cancer cell proliferation.

A Case of Community-Acquired Tuberculosis in an Infant Presenting with Pneumonia Refractory to Antibiotic Therapy.

Infant tuberculosis (TB) is a rare but potentially deadly infection and difficult to diagnose, especially in infants who may present with non-specific symptoms. Here, we report a case of an United States-born term infant with community-acquired miliary TB and no confirmed TB exposure history. The patient initially presented with respiratory distress at seven weeks of life with chest radiograph showing a right lower lobe (RLL) infiltrate. After failing multiple courses of treatment for community-acquired pneumonia and developing growth faltering, the patient had imaging findings suggestive of TB infection with CNS involvement. The diagnosis of TB was confirmed by QuantiFERON and purified protein derivative (PPD). In infants who fail conventional treatment for bacterial pneumonia, the differential should be broadened to consider alternative etiologies. Additionally, brain imaging should be performed in cases of disseminated TB despite negative cerebrospinal fluid (CSF) studies since these patients are at high risk of central nervous system (CNS) involvement. Topics: Tuberculosis, pneumonia, pediatrics, growth faltering.

The Effect of Hospital Visitor Policies on Patients, Their Visitors, and Health Care Providers During the COVID-19 Pandemic: A Systematic Review.

Health care policymaking during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has questioned the precedent of restricting hospital visitors. We aimed to synthesize available data describing the resulting impact on patient, family/visitor, and health care provider well-being. We systematically reviewed articles from the World Health Organization COVID-19 Global Literature on Coronavirus Disease Database published between December 2019 through April 2021. Included studies focused on hospitalized patients and reported 1 or more prespecified main or secondary outcome (coronavirus disease 2019 [COVID-19] disease transmission, global well-being, mortality, morbidity, or health care resource utilization). Two authors independently extracted data into a standardized form with a third author resolving discrepancies. A total of 1153 abstracts were screened, and 26 final full-text articles were included. Ten studies were qualitative, with 7 cohort studies, and no randomized controlled trials. Critically ill patients were the most represented (12 out of 26 studies). Blanket hospital visitor policies were associated with failure to address the unique needs of patients, their visitors, and health care providers in various clinical environments. Overall, a patient-centered, thoughtful, and nuanced approach to hospital visitor policies is likely to benefit all stakeholders while minimizing potential harms.

Assessment of clinical continuity strategies offered by dual-degree training programs in the USA.

Background: Integration of clinical skills during graduate training in dual-degree programs remains a challenge. The present study investigated the availability and self-perceived efficacy of clinical continuity strategies for dual-degree trainees preparing for clinical training. Methods: Survey participants were MD/DO-PhD students enrolled in dual-degree-granting institutions in the USA. The response rate was 95% of 73 unique institutions surveyed, representing 56% of the 124 MD-PhD and 7 DO-PhD recognized training programs. Respondents were asked to indicate the availability and self-perceived efficacy of each strategy. Results: Reported available clinical continuity strategies included clinical volunteering (95.6%), medical grand rounds (86.9%), mentored clinical experiences (84.2%), standardized patients/ practice Objective Structured Clinical Examinations (OSCEs) (70.3%), clinical case reviews (45.9%), clinical journal clubs (38.3%), and preclinical courses/review sessions (37.2%). Trainees rated standardized patients (µ = 6.98 ± 0.356), mentored clinical experiences (µ = 6.94 ± 0.301), clinical skills review sessions (µ = 6.89 ± 0.384), preclinical courses/review sessions (µ = 6.74 ± 0.482), and clinical volunteering (µ = 6.60 ± 0.369), significantly (p < 0.050) higher than clinical case review (µ = 5.34 ± 0.412), clinical journal club (µ = 4.75 ± 0.498), and medicine grand rounds (µ = 4.45 ± 0.377). Further, 84.4% of respondents stated they would be willing to devote at least 0.5-1 hour per week to clinical continuity opportunities during graduate training. Conclusion: Less than half of the institutions surveyed offered strategies perceived as the most efficacious in preparing trainees for clinical reentry, such as clinical skills review sessions. Broader implementation of these strategies could help better prepare dual-degree students for their return to clinical training.

Oncogenic B-Myb Is Associated With Deregulation of the DREAM-Mediated Cell Cycle Gene Expression Program in High Grade Serous Ovarian Carcinoma Clinical Tumor Samples.

Cell cycle control drives cancer progression and treatment response in high grade serous ovarian carcinoma (HGSOC). MYBL2 (encoding B-Myb), an oncogene with prognostic significance in several cancers, is highly expressed in most HGSOC cases; however, the clinical significance of B-Myb in this disease has not been well-characterized. B-Myb is associated with cell proliferation through formation of the MMB (Myb and MuvB core) protein complex required for transcription of mitotic genes. High B-Myb expression disrupts the formation of another transcriptional cell cycle regulatory complex involving the MuvB core, DREAM (DP, RB-like, E2F, and MuvB), in human cell lines. DREAM coordinates cell cycle dependent gene expression by repressing over 800 cell cycle genes in G0/G1. Here, we take a bioinformatics approach to further evaluate the effect of B-Myb expression on DREAM target genes in HGSOC and validate our cellular model with clinical specimens. We show that MYBL2 is highly expressed in HGSOC and correlates with expression of DREAM and MMB target genes in both The Cancer Genome Atlas (TCGA) as well as independent analyses of HGSOC primary tumors (N = 52). High B-Myb expression was also associated with poor overall survival in the TCGA cohort and analysis by a DREAM target gene expression signature yielded a negative impact on survival. Together, our data support the conclusion that high expression of MYBL2 is associated with deregulation of DREAM/MMB-mediated cell cycle gene expression programs in HGSOC and may serve as a prognostic factor independent of its cell cycle role. This provides rationale for further, larger scale studies aimed to determine the clinical predictive value of the B-Myb gene expression signature for treatment response as well as patient outcomes.

Role of phosphodiesterase 1 in the pathophysiology of diseases and potential therapeutic opportunities.

Cyclic nucleotide phosphodiesterases (PDEs) are superfamily of enzymes that regulate the spatial and temporal relationship of second messenger signaling in the cellular system. Among the 11 different families of PDEs, phosphodiesterase 1 (PDE1) sub-family of enzymes hydrolyze both 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP) in a mutually competitive manner. The catalytic activity of PDE1 is stimulated by their binding to Ca2+/calmodulin (CaM), resulting in the integration of Ca2+ and cyclic nucleotide-mediated signaling in various diseases. The PDE1 family includes three subtypes, PDE1A, PDE1B and PDE1C, which differ for their relative affinities for cAMP and cGMP. These isoforms are differentially expressed throughout the body, including the cardiovascular, central nervous system and other organs. Thus, PDE1 enzymes play a critical role in the pathophysiology of diseases through the fundamental regulation of cAMP and cGMP signaling. This comprehensive review provides the current research on PDE1 and its potential utility as a therapeutic target in diseases including the cardiovascular, pulmonary, metabolic, neurocognitive, renal, cancers and possibly others.

Restoring the DREAM Complex Inhibits the Proliferation of High-Risk HPV Positive Human Cells.

High-risk (HR) human papillomaviruses are known causative agents in 5% of human cancers including cervical, ano-genital and head and neck carcinomas. In part, HR-HPV causes cancer by targeting host-cell tumor suppressors including retinoblastoma protein (pRb) and RB-like proteins p107 and p130. HR-HPV E7 uses a LxCxE motif to bind RB proteins, impairing their ability to control cell-cycle dependent transcription. E7 disrupts DREAM (Dimerization partner, RB-like, E2F and MuvB), a transcriptional repressor complex that can include p130 or p107, but not pRb, which regulates genes required for cell cycle progression. However, it is not known whether disruption of DREAM plays a significant role in HPV-driven tumorigenesis. In the DREAM complex, LIN52 is an adaptor that binds directly to p130 via an E7-like LxSxE motif. Replacement of the LxSxE sequence in LIN52 with LxCxE (LIN52-S20C) increases p130 binding and partially restores DREAM assembly in HPV-positive keratinocytes and human cervical cancer cells, inhibiting proliferation. Our findings demonstrate that disruption of the DREAM complex by E7 is an important process promoting cellular proliferation by HR-HPV. Restoration of the DREAM complex in HR-HPV positive cells may therefore have therapeutic benefits in HR-HPV positive cancers.

The cell cycle regulatory DREAM complex is disrupted by high expression of oncogenic B-Myb.

Overexpression of the oncogene MYBL2 (B-Myb) is associated with increased cell proliferation and serves as a marker of poor prognosis in cancer. However, the mechanism by which B-Myb alters the cell cycle is not fully understood. In proliferating cells, B-Myb interacts with the MuvB core complex including LIN9, LIN37, LIN52, RBBP4, and LIN54, forming the MMB (Myb-MuvB) complex, and promotes transcription of genes required for mitosis. Alternatively, the MuvB core interacts with Rb-like protein p130 and E2F4-DP1 to form the DREAM complex that mediates global repression of cell cycle genes in G0/G1, including a subset of MMB target genes. Here, we show that overexpression of B-Myb disrupts the DREAM complex in human cells, and this activity depends on the intact MuvB-binding domain in B-Myb. Furthermore, we found that B-Myb regulates the protein expression levels of the MuvB core subunit LIN52, a key adapter for assembly of both the DREAM and MMB complexes, by a mechanism that requires S28 phosphorylation site in LIN52. Given that high expression of B-Myb correlates with global loss of repression of DREAM target genes in breast and ovarian cancer, our findings offer mechanistic insights for aggressiveness of cancers with MYBL2 amplification, and establish the rationale for targeting B-Myb to restore cell cycle control.

MuvB: A Key to Cell Cycle Control in Ovarian Cancer.

Cancer cells are characterized by uncontrolled proliferation, whereas the ability to enter quiescence or dormancy is important for cancer cell survival and disease recurrence. Therefore, understanding the mechanisms regulating cell cycle progression and exit is essential for improving patient outcomes. The MuvB complex of five proteins (LIN9, LIN37, LIN52, RBBP4, and LIN54), also known as LINC (LIN complex), is important for coordinated cell cycle gene expression. By participating in the formation of three distinct transcriptional regulatory complexes, including DREAM (DP, RB-like, E2F, and MuvB), MMB (Myb-MuvB), and FoxM1-MuvB, MuvB represents a unique regulator mediating either transcriptional activation (during S-G2 phases) or repression (during quiescence). With no known enzymatic activities in any of the MuvB-associated complexes, studies have focused on the therapeutic potential of protein kinases responsible for initiating DREAM assembly or downstream enzymatic targets of MMB. Furthermore, the mechanisms governing the formation and activity of each complex (DREAM, MMB, or FoxM1-MuvB) may have important consequences for therapeutic response. The MMB complex is associated with prognostic markers of aggressiveness in several cancers, whereas the DREAM complex is tied to disease recurrence through its role in maintaining quiescence. Here, we review recent developments in our understanding of MuvB function in the context of cancer. We specifically highlight the rationale for additional investigation of MuvB in high-grade serous ovarian cancer and the need for further translational research.

Training the physician-scientist: views from program directors and aspiring young investigators.

There is growing concern that the physician-scientist is endangered due to a leaky training pipeline and prolonged time to scientific independence (1). The NIH Physician-Scientist Workforce Working Group has concluded that as many as 1,000 individuals will need to enter the pipeline each year to sustain the workforce (2). Moreover, surveys of postgraduate training programs document considerable variability in disposition and infrastructure (3). Programs can be broadly grouped into two classes: physician-scientist training programs (PSTPs) that span residency and fellowship training, and research-in-residency programs (RiRs), which are limited to residency but trainees are able to match into PSTPs upon transitioning to fellowship (Figure 1). Funding sources for RiRs and PSTPs are varied and include NIH KL2 and T32 awards, charitable foundations, philanthropy, and institutional support. Furthermore, standards for research training and tools for evaluating programmatic success are lacking. Here, we share consensus generated from iterative workshops hosted by the Alliance of Academic Internal Medicine (AAIM) and the student-led American Physician Scientists Association (APSA).

Structural basis for LIN54 recognition of CHR elements in cell cycle-regulated promoters.

The MuvB complex recruits transcription factors to activate or repress genes with cell cycle-dependent expression patterns. MuvB contains the DNA-binding protein LIN54, which directs the complex to promoter cell cycle genes homology region (CHR) elements. Here we characterize the DNA-binding properties of LIN54 and describe the structural basis for recognition of a CHR sequence. We biochemically define the CHR consensus as TTYRAA and determine that two tandem cysteine rich regions are required for high-affinity DNA association. A crystal structure of the LIN54 DNA-binding domain in complex with a CHR sequence reveals that sequence specificity is conferred by two tyrosine residues, which insert into the minor groove of the DNA duplex. We demonstrate that this unique tyrosine-mediated DNA binding is necessary for MuvB recruitment to target promoters. Our results suggest a model in which MuvB binds near transcription start sites and plays a role in positioning downstream nucleosomes.

Non-small cell lung cancer is susceptible to induction of DNA damage responses and inhibition of angiogenesis by telomere overhang oligonucleotides.

Exposure of the telomere overhang acts as a DNA damage signal, and exogenous administration of an 11-base oligonucleotide homologous to the 3'-telomere overhang sequence (T-oligo) mimics the effects of overhang exposure by inducing senescence and cell death in non-small cell lung cancer (NSCLC) cells, but not in normal bronchial epithelial cells. T-oligo-induced decrease in cellular proliferation in NSCLC is likely directed through both p53 and its homolog, p73, with subsequent induction of senescence and expression of senescence-associated proteins, p21, p33(ING), and p27(Kip1) both in vivo and in vitro. Additionally, T-oligo decreases tumor size and inhibits angiogenesis through decreased VEGF signaling and increased TSP-1 expression.