Hot off the presses! Sep 01 Trends Cell Biol

The Sep 01 issue of the Trends Cell Biol is now up on Pubget (About Trends Cell Biol): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Contents page + Editorial Board
  - Trends Cell Biol 21(9):i (2011)
  
• Productive tension: force-sensing and homeostasis of cell–cell junctions
  - Trends Cell Biol 21(9):499-505 (2011)
  Cell–cell contacts are major determinants of tissue organization in both health and disease. Adhesive interactions, especially those mediated by classical cadherin receptors, influence cell–cell recognition and tissue patterning during development. Conversely, cadherin dysfunction promotes tumor progression to invasion and metastasis. Over the past three decades, we have learnt a great deal about the molecular mechanisms responsible for cadherin-based cell–cell interactions. Yet our knowledge remains incomplete. The intersection between cell biology and mechanical forces has long been suspected to be an important missing factor in understanding cadherin biology. However, tangible evidence remained elusive until recently, when several reports began to elucidate the role of cadherins and the cytoskeleton in mechanotransduction. In this review, we examine these advances and discuss their implications.
• The SecY complex: conducting the orchestra of protein translocation
  - Trends Cell Biol 21(9):506-514 (2011)
  Like the conductor of an orchestra, the Sec protein translocation channel is the platform needed to bring together the many different players required for the constitutive and obligatory process of protein transport. This conserved membrane channel, termed SecY in bacteria and Sec61 in eukaryotes, creates a ubiquitous protein-conducting pathway by which thousands of newly synthesized polypeptides make their way through the lipid bilayer. The channel is not a simple passive pore, however; it displays remarkable complexity by interacting with numerous soluble partners, including SecA, Syd, FtsY and the ribosome in bacteria. For several decades, scientists have been fascinated by the sophistication and versatility of this transport channel. In this review, we cover the current state of the field including some of the newest and most exciting findings on channel structure and mechanism of action.
• Membrane-trafficking sorting hubs: cooperation between PI4P and small GTPases at the trans-Golgi network
  - Trends Cell Biol 21(9):515-525 (2011)
  Cell polarity in eukaryotes requires constant sorting, packaging and transport of membrane-bound cargo within the cell. These processes occur in two sorting hubs: the recycling endosome for incoming material and the trans-Golgi network for outgoing material. Phosphatidylinositol 3-phosphate and phosphatidylinositol 4-phosphate are enriched at the endocytic and exocytic sorting hubs, respectively, where they act together with small GTPases to recruit factors to segregate cargo and regulate carrier formation and transport. In this review, we summarize the current understanding of how these lipids and GTPases regulate membrane trafficking directly, emphasizing the recent discoveries of phosphatidylinositol 4-phosphate functions at the trans-Golgi network.
• Fly meets yeast: checking the correct orientation of cell division
  - Trends Cell Biol 21(9):526-533 (2011)
  Cell division is generally thought to be a process that produces an exact copy of the mother cell by precisely replicating its genomic DNA, doubling organelles, and segregating them into two cells. Many cell types from bacteria to human cells divide asymmetrically, however, to generate daughter cells with distinct characteristics. Such asymmetric divisions are fundamental to the lifespan of a cell, to embryonic development, and to stem cell homeostasis. Asymmetric division requires coordination of cellular asymmetry and the cell division machinery. Accumulating evidence suggests that the basic molecular mechanisms that govern this process are conserved from yeast to humans. In this review we highlight similarities in the mechanisms of asymmetric cell division in yeast and Drosophila male germline stem cells (GSCs) in the hope of extracting common themes underlying several systems.
• Histone ADP-ribosylation in DNA repair, replication and transcription
  - Trends Cell Biol 21(9):534-542 (2011)
  Most published work on post-translational histone modifications focuses on small covalent alterations such as acetylation, methylation and phosphorylation. By contrast, fewer data are available on the modification of histones by ADP-ribose. Discussion of the biological significance of histone ADP-ribosylation has often been restricted to functions of the modifying enzymes, rather than to histones as ADP-ribose acceptors. In particular, the identification of specific lysine residues as ADP-ribose acceptor sites in histones and the identification of ADP-ribose binding modules raise this modification to a par with acetylation, methylation or phosphorylation. We discuss here the functional aspects of histone ADP-ribosylation and its influence on DNA repair, replication and transcription.
• Biological hydrogels as selective diffusion barriers
  - Trends Cell Biol 21(9):543-551 (2011)
  The controlled exchange of molecules between organelles, cells, or organisms and their environment is crucial for life. Biological gels such as mucus, the extracellular matrix (ECM), and the biopolymer barrier within the nuclear pore are well suited to achieve such a selective exchange, allowing passage of particular molecules while rejecting many others. Although hydrogel-based filters are integral parts of biology, clear concepts of how their barrier function is controlled at a microscopic level are still missing. We summarize here our current understanding of how selective filtering is established by different biopolymer-based hydrogels. We ask if the modulation of microscopic particle transport in biological hydrogels is based on a generic filtering principle which employs biochemical/biophysical interactions with the filtered molecules rather than size-exclusion effects.
• Deciphering condensin action during chromosome segregation
  - Trends Cell Biol 21(9):552-559 (2011)
  The correct segregation of eukaryotic genomes requires the resolution of sister DNA molecules and their movement into opposite halves of the cell before cell division. The dynamic changes chromosomes need to undergo during these events depend on the action of a multi-subunit SMC (structural maintenance of chromosomes) protein complex named condensin, but its molecular function in chromosome segregation is still poorly understood. Recent studies suggest that condensin has a role in the removal of sister chromatid cohesin, in sister chromatid decatenation by topoisomerases, and in the structural reconfiguration of mitotic chromosomes. In this review we discuss possible mechanisms that could explain the variety of condensin actions during chromosome segregation.