Jun dimerization protein 2 controls hypoxia-induced replicative senescence via both the p16Ink4a-pRb and Arf-p53 pathways

Jun Dimerization Protein 2 (JDP2) Increases p53 Transactivation by Decreasing MDM2

The AP-1 protein complex primarily consists of several proteins from the c-Fos, c-Jun, activating transcription factor (ATF), and Jun dimerization protein (JDP) families. JDP2 has been shown to interact with the cAMP response element (CRE) site present in many cis-elements of downstream target genes. JDP2 has also demonstrates important roles in cell-cycle regulation, cancer development and progression, inhibition of adipocyte differentiation, and the regulation of antibacterial immunity and bone homeostasis. JDP2 and ATF3 exhibit significant similarity in their C-terminal domains, sharing 60-65% identities. Previous studies have demonstrated that ATF3 is able to influence both the transcriptional activity and p53 stability via a p53-ATF3 interaction. While some studies have shown that JDP2 suppresses p53 transcriptional activity and in turn, p53 represses JDP2 promoter activity, the direct interaction between JDP2 and p53 and the regulatory role of JDP2 in p53 transactivation have not been explored. In the current study, we provide evidence, for the first time, that JDP2 interacts with p53 and regulates p53 transactivation. First, we demonstrated that JDP2 binds to p53 and the C-terminal domain of JDP2 is crucial for the interaction. Second, in p53-null H1299 cells, JDP2 shows a robust increase of p53 transactivation in the presence of p53 using p53 (14X)RE-Luc. Furthermore, JDP2 and ATF3 together additively enhance p53 transactivation in the presence of p53. While JDP2 can increase p53 transactivation in the presence of WT p53, JDP2 fails to enhance transactivation of hotspot mutant p53. Moreover, in CHX chase experiments, we showed that JDP2 slightly enhances p53 stability. Finally, our findings indicate that JDP2 has the ability to reverse MDM2-induced p53 repression, likely due to decreased levels of MDM2 by JDP2. In summary, our results provide evidence that JDP2 directly interacts with p53 and decreases MDM2 levels to enhance p53 transactivation, suggesting that JDP2 is a novel regulator of p53 and MDM2.

The Senescence Markers p16INK4A, p14ARF/p19ARF, and p21 in Organ Development and Homeostasis

It is widely accepted that senescent cells accumulate with aging. They are characterized by replicative arrest and the release of a myriad of factors commonly called the senescence-associated secretory phenotype. Despite the replicative cell cycle arrest, these cells are metabolically active and functional. The release of SASP factors is mostly thought to cause tissue dysfunction and to induce senescence in surrounding cells. As major markers for aging and senescence, p16INK4, p14ARF/p19ARF, and p21 are established. Importantly, senescence is also implicated in development, cancer, and tissue homeostasis. While many markers of senescence have been identified, none are able to unambiguously identify all senescent cells. However, increased levels of the cyclin-dependent kinase inhibitors p16INK4A and p21 are often used to identify cells with senescence-associated phenotypes. We review here the knowledge of senescence, p16INK4A, p14ARF/p19ARF, and p21 in embryonic and postnatal development and potential functions in pathophysiology and homeostasis. The establishment of senolytic therapies with the ultimate goal to improve healthy aging requires care and detailed knowledge about the involvement of senescence and senescence-associated proteins in developmental processes and homeostatic mechanism. The review contributes to these topics, summarizes open questions, and provides some directions for future research.

Chronic exposure to PFO4DA and PFO5DoDA, two perfluoroalkyl ether carboxylic acids (PFECAs), suppresses hepatic stress signals and disturbs glucose and lipid metabolism in male mice

Perfluoroalkyl ether carboxylic acids (PFECAs), including PFO4DA and PFO5DoDA, have been found in both surface water and volunteer blood samples from polluted regions. However, little knowledge is available on their potential bioaccumulation and health risk. In the present study, the half-lives of PFO4DA and PFO5DoDA in male mouse serum were 24 h and nearly 43 d, respectively, indicating markedly increased difficulty in eliminating PFO5DoDA from the body. After 140 d daily exposure both PFO4DA and PFO5DoDA (10 μg/kg/d) increased body weight. Hepatomegaly was the most sensitive phenomenon after exposure treatment, with occurrence even in the 2 μg/kg/d exposure groups. RNA-seq analysis supported a similar but stronger effect of PFO5DoDA compared with PFO4DA. A wide array of genes involved in stimulus sensing and response were suppressed. In addition to weight gain, hyperglycemia was also observed after treatment. Increased glucose and decreased pyruvate and lactate levels in the liver supported a reduction in glycolysis, consistent with the reduction in the key regulator Pfkfb3. In conclusion, chronic PFO4DA and PFO5DoDA exposure suppressed stress signals and disturbed glucose and lipid metabolism in the liver. The longer serum half-life and stronger hepatic bioaccumulation of PFO5DoDA, at least partially, contributed to its stronger hepatotoxicity than that of PFO4DA.

Possibility of inducing tumor cell senescence during therapy

The treatment options for cancer include surgery, radiotherapy and chemotherapy. However, the traditional approach of high-dose chemotherapy brings tremendous toxic side effects to patients, as well as potentially causing drug resistance. Drug resistance affects cell proliferation, cell senescence and apoptosis. Cellular senescence refers to the process in which cells change from an active proliferative status to a growth-arrested status. There are multiple factors that regulate this process and cellular senescence is activated by various pathways. Senescent cells present specific characteristics, such as an increased cell volume, flattened cell body morphology, ceased cell division and the expression of β-galactosidase. Tumor senescence can be categorized into replicative senescence and premature senescence. Cellular senescence may inhibit the occurrence and development of tumors, serving as an innovative strategy for the treatment of cancer. The present review mainly focuses on senescent biomarkers, methods for the induction of cellular senescence and its possible application in the treatment of cancer.

Hypoxia in Cell Reprogramming and the Epigenetic Regulations

Cellular reprogramming is a fundamental topic in the research of stem cells and molecular biology. It is widely investigated and its understanding is crucial for learning about different aspects of development such as cell proliferation, determination of cell fate and stem cell renewal. Other factors involved during development include hypoxia and epigenetics, which play major roles in the development of tissues and organs. This review will discuss the involvement of hypoxia and epigenetics in the regulation of cellular reprogramming and how interplay between each factor can contribute to different cellular functions as well as tissue regeneration.