No abstract

Human renal clear cell carcinoma (RCC) is frequently associated with loss of the von Hippel-Lindau (VHL)tumor suppressor (pVHL), which inhibits ubiquitylation and degradation of the alpha subunits of hypoxiainducible transcription factor. pVHL also ubiquitylates the large subunit of RNA polymerase II, Rpb1, phosphorylated on serine 5 (Ser5) within the C-terminal domain (CTD). A hydroxylated proline 1465 within an LXXLAP motif located N-terminal to the CTD allows the interaction of Rpb1 with pVHL. Here we report that in RCC cells, pVHL regulates expression of Rpb1 and is necessary for low-grade oxidative-stress-induced recruitment of Rpb1 to the DNA-engaged fraction and for its P1465 hydroxylation, phosphorylation, and nondegradative ubiquitylation. Egln-9-type prolyl hydroxylases, PHD1 and PHD2, coimmunoprecipitated with Rpb1 in the chromatin fraction of VHL ؉ RCC cells in response to oxidative stress, and PHD1 was necessary for P1465 hydroxylation while PHD2 had an inhibitory effect. P1465 hydroxylation was required for oxidativestress-induced Ser5 phosphorylation of Rpb1. Importantly, overexpression of wild-type Rpb1 stimulated formation of kidney tumors by VHL ؉ cells, and this effect was abolished by P1465A mutation of Rpb1. These data indicate that through this novel pathway involving P1465 hydroxylation and Ser5 phosphorylation of Rbp1, pVHL may regulate tumor growth.pVHL is the main tumor suppressor for which loss of activity is causatively linked to renal clear cell carcinoma (RCC), the most malignant and common form of kidney cancer. The VHL gene is mutated or hypermethylated in about 40 to 70% of sporadic RCC. Hereditary loss of pVHL function in von Hippel-Lindau (VHL) disease also results in highly vascularized RCC and capillary tumors of other organs, such as hemangioblastoma of the central nervous system and retinal angioma (19,20). A body of experimental evidence, based on a subcutaneous xenograft model system, supports the idea that accumulation of the alpha subunit of the hypoxia-inducible transcription factor (HIF) HIF-2␣ and induction of HIF target gene products, resulting from the loss of pVHL-mediated ubiquitylation, are necessary and sufficient to promote growth of RCC tumors (22,23). HIF activation has also been demonstrated as an early tumorigenesis event in kidneys from VHL patients (32). Biochemically, pVHL is the substrate-recognizing component of a multiprotein E3 ubiquitin ligase complex containing elongins C and B, Cullin 2, and the RING-H2 finger protein Rbx-1 (for a review, see reference 19). pVHL-dependent ubiquitylation of HIF-␣s is preceded by hydroxylation of conserved proline residues located within LXXLAP motifs (16,17) by the O 2 -, Fe(II)-, and oxyglutarate-regulated Egl-9-type proline hydroxylases (PHDs) (7). Thus, an important aspect of pVHL's tumor suppressing activity is the prevention of HIF-␣ accumulation, which in turn suppresses induction of the HIF target genes. Clearly, however, pVHL activity is not limited to regulation of HIFs. Other targets of pVHL-associated E...

Saccharomyces cerevisiae yeast cells encapsulated with pH-responsive synthetic nanoshells from lightly cross-linked polymethacrylic acid showed a high viability rate of around 90%, an indication of high biocompatibility of synthetic pH-responsive shells. We demonstrated that increasing pH above the isoelectric point of the polymer shell leads to a delay in growth rate; however, it does not affect the expression of enhanced green fluorescent protein. We suggest that progressive ionization and charge accumulation within the synthetic shells evoke a structural change in the outer shells which affect the membrane transport. This change facilitates the ability to manipulate growth kinetics and functionality of the cells with the surrounding environment. We observed that hollow layer-by layer nanoshells showed a remarkable degree of reversible swelling/deswelling over a narrow pH range (pH 5.0-6.0), but their assembly directly on the cell surface resulted in the suppression of large dimensional changes. We suggest that the variation in surface charges caused by deprotonation/protonation of carboxylic groups in the nanoshells controlled cell growth and cell function, which can be utilized for external chemical control of cell-based biosensors.

Cell-free protein synthesis (CFPS) platforms, once primarily a research tool to produce difficult to express proteins, are increasingly being pursued by the synthetic biology community for applications including biomanufacturing, rapid screening systems, and field-ready sensors. While consistency within individual studies is apparent in the literature, challenges with reproducing results between laboratories, or even between individuals within a laboratory, are discussed openly by practitioners. As the field continues to grow and move toward applications, a quantitative understanding of expected variability for CFPS and the relative contribution of underlying sources will become increasingly important. Here we offer the first quantitative assessment of interlaboratory variability in CFPS. Three laboratories implemented a single CFPS protocol and performed a series of exchanges, both of material and personnel, designed to quantify relative contributions to variability associated with the site, operator, cell extract preparation, and supplemental reagent preparation. We found that materials prepared at each laboratory, exchanged pairwise, and tested at each site resulted in 40.3% coefficient of variation compared to 7.64% for a single operator across days using a single set of materials. Reagent preparations contributed significantly to observed variability; extract preparations, however, surprisingly did not explain any of the observed variability, even when prepared in different laboratories by different operators. Subsequent exchanges showed that both the site and the operator each contributed to observed interlaboratory variability. In addition to providing the first quantitative assessment of interlaboratory variability in CFPS, these results establish a baseline for individual operator variability across days that can be used as an initial benchmark for community-driven standardization efforts. We anticipate that our results will narrow future avenues of investigation to develop best practices that will ultimately drive down interlaboratory variability, accelerating research progress and informing the suitability of CFPS for real-world applications.

This study introduces double-brush designs of functionalized silk polyelectrolytes based upon regenerated silk fibroin (SF), which is modified with poly-L-lysine (SF-PLL), poly-L-glutamic acid (SF-PGA), and poly(ethylene glycol) (PEG) side chains with different grafting architecture and variable amino acid-PEG graft composition for cell encapsulation. The molecular weight of poly amino acids (length of side chains), molecular weight and degree of PEG grafting (D) were varied in order to assess the formation of cytocompatible and robust layer-by-layer (LbL) shells on two types of bacterial cells (Gram-negative and Gram-positive bacteria). We observed that shells assembled with charged polycationic amino acids adversely effected the properties of microbial cells while promoting the formation of large cell aggregates. In contrast, hydrogen-bonded shells with high PEG grafting density were the most cytocompatible, while promoting formation of stable colloidal suspensions of individual cell encapsulates. The stability to degradation of silk shells (under standard cell incubation procedure) was related to the intrinsic properties of thermodynamic bonding forces, with shells based on electrostatic interactions having stronger resistance to deterioration compared to pure hydrogen-bonded silk shells. By optimizing the charge density of silk polyelectrolytes brushes, as well as the length and the degree of PEG side grafts, robust and cytocompatible cell coatings were engineered that can control aggregation of cells for biosensor devices and other potential biomedical applications.