The Journal of Cell Biology current issueThe Journal of Cell Biology RSS feed -- current issueThe AAA ATPase Rix7 powers progression of ribosome biogenesis by stripping Nsa1 from pre-60S particles- June 16, 2008 Ribosome biogenesis takes place successively in the nucleolar, nucleoplasmic, and cytoplasmic compartments. Numerous nonribosomal factors transiently associate with the nascent ribosomes, but the mechanisms driving ribosome formation are mostly unknown. Here, we show that an energy-consuming enzyme, the AAA-type (ATPases associated with various cellular activities) ATPase Rix7, restructures a novel pre-60S particle at the transition from the nucleolus to nucleoplasm. Rix7 interacts genetically..http://www.jcb.org/cgi/content/short/181/6/935?rss=1 Spatial mapping of splicing factor complexes involved in exon and intron definition- June 16, 2008 We have analyzed the interaction between serinearginine-rich (SR) proteins and splicing components that recognize either the 5' or 3' splice site. Previously, these interactions have been extensively characterized biochemically and are critical for both intron and exon definition. We use fluorescence resonance energy transfer (FRET) microscopy to identify interactions of individual SR proteins with the U1 small nuclear ribonucleoprotein (snRNP)–associated 70-kD protein (U1 70K) and with...http://www.jcb.org/cgi/content/short/181/6/921?rss=1 Alison Frand: Breaking out new ideas on molting- June 16, 2008http://www.jcb.org/cgi/content/short/181/6/876?rss=1 Cytokine secretion requires phosphatidylcholine synthesis- June 16, 2008 Choline cytidylyltransferase (CCT) is the rate-limiting enzyme in the phosphatidylcholine biosynthetic pathway. Here, we demonstrate that CCT-mediated phosphatidylcholine synthesis is required to maintain normal Golgi structure and function as well as cytokine secretion from the Golgi complex. CCT is localized to the trans-Golgi region and its expression is increased in lipopolysaccharide (LPS)-stimulated wild-type macrophages. Although LPS triggers transient reorganization of Golgi morphology..http://www.jcb.org/cgi/content/short/181/6/945?rss=1 Cell motility through plasma membrane blebbing- June 16, 2008 Plasma membrane blebs are dynamic cytoskeleton-regulated cell protrusions that have been implicated in apoptosis, cytokinesis, and cell movement. Influencing Rho–guanosine triphosphatase activities and subsequent actomyosin dynamics appears to constitute a core component for bleb formation. In this paper, we discuss recent evidence in support of a central role of nonapoptotic membrane blebbing for cell migration and cancer cell invasion as well as advances in our understanding of the...http://www.jcb.org/cgi/content/short/181/6/879?rss=1 Regulation of neural progenitor cell state by ephrin-B- June 16, 2008 Maintaining a balance between self-renewal and differentiation in neural progenitor cells during development is important to ensure that correct numbers of neural cells are generated. We report that the ephrin-B–PDZ-RGS3 signaling pathway functions to regulate this balance in the developing mammalian cerebral cortex. During cortical neurogenesis, expression of ephrin-B1 and PDZ-RGS3 is specifically seen in progenitor cells and is turned off at the onset of neuronal differentiation....http://www.jcb.org/cgi/content/short/181/6/973?rss=1 Centromere mitotic recombination in mammalian cells- June 16, 2008 Centromeres are special structures of eukaryotic chromosomes that hold sister chromatid together and ensure proper chromosome segregation during cell division. Centromeres consist of repeated sequences, which have hindered the study of centromere mitotic recombination and its consequences for centromeric function. We use a chromosome orientation fluorescence in situ hybridization technique to visualize and quantify recombination events at mouse centromeres. We show that centromere mitotic...http://www.jcb.org/cgi/content/short/181/6/885?rss=1 Regulation of RhoA-dependent ROCKII activation by Shp2- June 16, 2008 Contractile forces mediated by RhoA and Rho kinase (ROCK) are required for a variety of cellular processes, including cell adhesion. In this study, we show that RhoA-dependent ROCKII activation is negatively regulated by phosphorylation at a conserved tyrosine residue (Y722) in the coiled-coil domain of ROCKII. Tyrosine phosphorylation of ROCKII is increased with cell adhesion, and loss of Y722 phosphorylation delays adhesion and spreading on fibronectin, suggesting that this modification is...http://www.jcb.org/cgi/content/short/181/6/999?rss=1 Mps1 kinase activity restrains anaphase during an unperturbed mitosis and targets Mad2 to kinetochores- June 16, 2008 Mps1 is an upstream component of the spindle assembly checkpoint, which, in human cells, is required for checkpoint activation in response to spindle damage but not apparently during an unperturbed mitosis. Mps1 also recruits Mad1 and Mad2 to kinetochores. However, whether the enzymatic activity of Mps1 is required for these processes is unclear. To address this question, we established an RNA interference (RNAi) complementation assay. Repression of Mps1 triggers premature anaphase, often with..http://www.jcb.org/cgi/content/short/181/6/893?rss=1 |