Dissecting ubiquitin signaling with linkage-defined and protease resistant ubiquitin chains.

Ubiquitylation is a complex posttranslational protein modification and deregulation of this pathway has been associated with different human disorders. Ubiquitylation comes in different flavors: Besides mono-ubiquitylation, ubiquitin chains of various topologies are formed on substrate proteins. The fate of ubiquitylated proteins is determined by the linkage-type of the attached ubiquitin chains, however, the underlying mechanism is poorly characterized. Herein, we describe a new method based on codon expansion and click-chemistry-based polymerization to generate linkage-defined ubiquitin chains that are resistant to ubiquitin-specific proteases and adopt native-like functions. The potential of these artificial chains for analyzing ubiquitin signaling is demonstrated by linkage-specific effects on cell-cycle progression.

Increasing collaboration between China and India in the environmental sciences to foster global sustainability.

As the two largest countries by population, China and India have pervasive effects on the ecosphere. Because of their human population size and long international boundary, they share biodiversity and the threats to it, as well as crops, pests and diseases. We ranked the two countries on a variety of environmental challenges and solutions, illustrating quantitatively their environmental footprint and the parallels between them regarding the threats to their human populations and biodiversity. Yet we show that China and India continue to have few co-authorships in environmental publications, even as their major funding for scientific research has expanded. An agenda for collaboration between China and India can start with the shared Himalaya, linking the countries' scientists and institutions. A broader agenda can then be framed around environmental challenges that have regional patterns. Coordinated and collaborative research has the potential to improve the two countries' environmental performance, with implications for global sustainability.

RETRACTED: The Anaphase-Promoting Complex/Cyclosome Is Essential for Entry into Meiotic M-Phase.

Vertebrate immature oocytes are arrested at prophase of meiosis I (MI). Hormonal stimulation breaks this prophase-I arrest and induces re-entry into MI. The mechanism underlying meiotic resumption remains largely elusive. Here, we demonstrate that the anaphase-promoting complex/cyclosome (APC/C) in complex with Cdh1 has an unexpected function in meiosis in that it is essential for meiotic resumption. We identify the catalytic subunit of protein phosphatase 6 (PP6c) as the critical substrate whose APC/C(Cdh1)-mediated destruction is a prerequisite for the re-entry of immature Xenopus laevis oocytes into MI. Preventing PP6c destruction impairs activating autophosphorylation of Aurora A, a cell-cycle kinase critical for meiotic translation. Restoring meiotic translation rescues the meiotic resumption defect of Cdh1-depleted oocytes. Thus, our studies discover that the essential function of the APC/C in triggering cell-cycle transitions is not limited to M-phase exit but also applies to entry into meiotic M-phase, and identify a crucial APC/C-PP6c-Aurora A axis in the resumption of female meiosis.