Microbial expansion following faunal mass extinctions in Earth history can be studied by petrographic examination of microbialites (microbial crusts) or well-preserved organic-walled microbes. However, where preservation is poor, quantification of microbial communities can be problematic. We have circumvented this problem by adopting a lipid biomarker-based approach to evaluate microbial community changes across the Permo/Triassic (P/Tr) boundary at Meishan in South China. We present here a biomarker stratigraphic record showing episodic microbial changes coupled with a high-resolution record of invertebrate mass extinction. Variation in the microbial community structure is characterized by the 2-methylhopane (2-MHP) index (a ratio of the abundance of cyanobacterial biomarkers to more general bacterial biomarkers). Two episodes of faunal mass extinction were each preceded by minima in the 2-MHP index, followed by strong maxima, likely reflecting microbial responses to the catastrophic events that caused the extinction and initiated ecosystem changes. Hence, both cyanobacterial biomarker and invertebrate fossil records provide evidence for two episodes of biotic crisis across the P/Tr boundary.

Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore, a multiprotein complex assembled onto centromeric DNA of the chromosome. Here we show that Zwint-1 is required and is sufficient for kinetochore localization of Zeste White 10 (ZW10) in HeLa cells. Zwint-1 specifies the kinetochore association of ZW10 by interacting with its N-terminal domain. Suppression of synthesis of Zwint-1 by small interfering RNA abolishes the localization of ZW10 to the kinetochore, demonstrating the requirement of Zwint-1 for ZW10 kinetochore localization. In addition, depletion of Zwint-1 affects no mitotic arrest but causes aberrant premature chromosome segregation. These Zwint-1-suppressed cells display chromosome bridge phenotype with sister chromatids inter-connected. Moreover, Zwint-1 is required for stable association of CENP-F and dynamitin but not BUB1 with the kinetochore. Finally, our studies show that Zwint-1 is a new component of the mitotic checkpoint, as cells lacking Zwint-1 fail to arrest in mitosis when exposed to microtubule inhibitors, yielding interphase cells with multinuclei. As ZW10 and Zwint-1 are absent from yeast, we reasoned that metazoans evolved an elaborate spindle checkpoint machinery to ensure faithful chromosome segregation in mitosis.Chromosome movements during mitosis are governed by the interaction of spindle microtubules with a specialized chromosome domain located within the centromere. This specialized region, called the kinetochore (1, 2), is the site for spindle microtubule-centromere association. In addition to providing a physical link between chromosomes and spindle microtubules, the kinetochore has an active function in chromosomal segregation through microtubule motors and spindle checkpoint sensors located at or near it (3-5).Eukaryotic organisms require extraordinary fidelity in chromosome segregation during meiosis and mitosis as aberrant chromosome segregation can be catastrophic to an organism or its progeny. One of the evolutionarily conserved multiprotein complexes essential for the fidelity of chromosome segregation contains several proteins, including ZW10 1 (Zeste White 10) and ROD (Rough Deal) (6 -8). Mutations in the Drosophila ZW10 or ROD genes cause similar defects, most noticeably in lagging chromatids that remain at the metaphase plate late in anaphase, leading to high levels of aneuploidy among daughter cells.ZW10 and ROD proteins display remarkable dynamics in their intracellular location during cell division (7, 9, 10). Both proteins accumulate strongly at the outer kinetochore plates during prometaphase. At metaphase, ZW10 and ROD depart from the kinetochores and relocate onto spindle microtubules. During anaphase, the proteins are no longer found on kinetochore microtubules and instead localize exclusively to the kinetochores of the separating chromosomes.Besides binding to ROD, ZW10 is responsible for localization of cytoplasmic dynein to kinetochores (10 -12) via a direct contact with dynamitin, a...

Ubiquitination and deubiquitination of receptor-interacting protein 1 (RIP1) play an important role in the positive and negative regulation of the tumor necrosis factor ␣ (TNF␣)-induced nuclear factor B (NF-B) activation. Using a combination of functional genomic and proteomic approaches, we have identified ubiquitin-specific peptidase 21 (USP21) as a deubiquitinase for RIP1. USP21 is constitutively associated with RIP1 and deubiquitinates RIP1 in vitro and in vivo. Notably, knockdown of USP21 in HeLa cells enhances TNF␣-induced RIP1 ubiquitination, IB kinase ␤ (IKK␤), and NF-B phosphorylation, inhibitor of NF-B ␣ (IB␣) phosphorylation and ubiquitination, as well as NF-B-dependent gene expression. Therefore, our results demonstrate that USP21 plays an important role in the down-regulation of TNF␣-induced NF-B activation through deubiquitinating RIP1. Transcription factor nuclear factor B (NF-B)3 plays an important role in controlling the expression of survival factors, cytokines, and proinflammatory molecules in a broad range of cellular responses (1-3). NF-B is sequestered in the cytoplasm by a family of inhibitory proteins called inhibitor of NF-B (IB) proteins in inactivated cells. Many intercellular stimuli are capable of triggering the activation of a signal transduction pathway that leads to the degradation of IB proteins through the 26 S proteasome (4 -6). Degradation of the IB proteins allows NF-B translocation from cytoplasm to the nucleus and activates the expression of the target genes (7).Upon binding of tumor necrosis factor ␣ (TNF␣), TNF receptor 1 (TNFR1) recruits several adaptor proteins, including receptorinteracting protein 1 (RIP1/RIPK1) and TNF receptor-associated factor 2 (TRAF2), to form a complex (8, 9). This TNFR1-associated complex initiates the activation of IB kinase (IKK), which phosphorylates IB protein and activates NF-B (10 -17).Protein ubiquitination is a crucial regulatory mechanism in various cellular processes, including cell cycle progression, the DNA damage response, and immune responses (18 -20). In the TNF␣-induced NF-B signal transduction pathway, the Lys 63 -linked polyubiquitination of RIP1 protein mediated by TRAF2 E3 ligase is essential for TNF␣-induced IKK/NF-B activation, whereas phosphorylation of the IB proteins by activated IKK leads to their Lys 48 -linked polyubiquitination, which labels it for its degradation by the 26 S proteasome (21).Several deubiquitinating enzymes, including CYLD, A20, Cezanne, ubiquitin-specific peptidase 15 (USP15), and USP31, have been suggested to be involved in the down-regulation of TNF␣-induced NF-B activation (22-26). However, it remains unclear how deubiquitination plays a role in the down-regulation of TNF␣-induced NF-B activation.The USPs belong to a subclass of the protein-deubiquitinating enzyme (DUB) superfamily that are categorized into five subclasses based on their ubiquitin-protease domains in the human genome and have been shown to be involved in a broad range of biological activities (27). Even though the USP subclass o...

High abundance and widespread distribution of the archaeal phylum Bathyarchaeota in marine environment have been recognized recently, but knowledge about Bathyarchaeota in terrestrial settings and their correlation with environmental parameters is fairly limited. Here we reported the abundance of Bathyarchaeota members across different ecosystems and their correlation with environmental factors by constructing 16S rRNA clone libraries of peat from the Dajiuhu Peatland, coupling with bioinformatics analysis of 16S rRNA data available to date in NCBI database. In total, 1456 Bathyarchaeota sequences from 28 sites were subjected to UniFrac analysis based on phylogenetic distance and multivariate regression tree analysis of taxonomy. Both phylogenetic and taxon-based approaches showed that salinity, total organic carbon and temperature significantly influenced the distribution of Bathyarchaeota across different terrestrial habitats. By applying the ecological concept of ‘indicator species’, we identify 9 indicator groups among the 6 habitats with the most in the estuary sediments. Network analysis showed that members of Bathyarchaeota formed the “backbone” of archaeal community and often co-occurred with Methanomicrobia. These results suggest that Bathyarchaeota may play an important ecological role within archaeal communities via a potential symbiotic association with Methanomicrobia. Our results shed light on understanding of the biogeography, potential functions of Bathyarchaeota and environment conditions that influence Bathyarchaea distribution in terrestrial settings.