Hot off the presses! May 01 Trends Cell Biol

The May 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:

• Editorial Board
  - Trends Cell Biol 19(5):i (2009)
  
• A post-translational modification code for transcription factors: sorting through a sea of signals
  - Trends Cell Biol 19(5):189-197 (2009)
  Cellular responses to environmental or physiological cues rely on transduction pathways that must ensure discrimination between different signals. These cascades 'crosstalk' and lead to a combinatorial regulation. This often results in different combinations of post-translational modifications (PTMs) on target proteins, which might act as a molecular barcode. Although appealing, the idea of the existence of such a code for transcription factors is debated. Using general arguments and recent evidence, we propose that a PTM code is not only possible but necessary in the context of transcription factors regulating multiple processes. Thus, the coding potential of PTM combinations should both provide a further layer of information integration from several transduction pathways and warrant highly specific cellular outputs.
• Merlin and the ERM proteins – regulators of receptor distribution and signaling at the cell cortex
  - Trends Cell Biol 19(5):198-206 (2009)
  Recent studies highlight the importance of the distribution of membrane receptors in controlling receptor output and in contributing to complex biological processes. The cortical cytoskeleton is known to affect membrane protein distribution but the molecular basis of this is largely unknown. Here, we discuss the functions of Merlin and the ERM proteins both in linking membrane proteins to the underlying cortical cytoskeleton and in controlling the distribution of and signaling from membrane receptors. We also propose a model that could account for the intricacies of Merlin function across model organisms.
• Crosstalk between histone modifications during the DNA damage response
  - Trends Cell Biol 19(5):207-217 (2009)
  Chromatin structure has a crucial role in processes of metabolism, including transcription, DNA replication and DNA damage repair. An evolutionarily conserved variant of histone H2A, called H2AX, is one of the key components of chromatin. H2AX becomes rapidly phosphorylated on chromatin surrounding DNA double-strand breaks (DSBs). Recent studies have shown that H2AX and other components of damaged chromatin also become modified by acetylation and ubiquitylation. This review discusses how specific combinations of histone modifications affect the accumulation and function of DNA repair factors (MDC1, RNF8, RNF168, 53BP1, BRCA1) and chromatin remodeling complexes (INO80, SWR1, TIP60-p400) at DSBs. These collectively regulate DSB repair and checkpoint arrest, avoiding genomic instability and oncogenic transformation in higher eukaryotes.
• Spine microdomains for postsynaptic signaling and plasticity
  - Trends Cell Biol 19(5):218-227 (2009)
  Changes in the molecular composition and signaling properties of excitatory glutamatergic synapses onto dendritic spines mediate learning-related plasticity in the mammalian brain. This molecular adaptation serves as the most celebrated cell biological model for learning and memory. Within their micron-sized dimensions, dendritic spines restrict the diffusion of signaling molecules and spatially confine the activation of signal transduction pathways. Much of this local regulation occurs by spatial compartmentalization of glutamate receptors. Here, we review recently identified cell biological mechanisms regulating glutamate receptor mobility within individual dendritic spines. We discuss the emerging functions of glutamate receptors residing within sub-spine microdomains and propose a model for distinct signaling platforms with specialized functions in synaptic plasticity.
• Feeling green: mechanosensing in plants
  - Trends Cell Biol 19(5):228-235 (2009)
  Owing to the sessile nature of their lifestyle, plants have to respond to a wide range of signals, such as the force of the wind or the impedance of the soil, to entrain their development to prevailing environmental conditions. Indeed, mechanically responsive growth has been documented in plants for many years but new work on lateral root formation strongly supports the idea that biophysical forces can elicit complete de novo developmental programs. In addition, only recently have molecular candidates for plant mechanosensors emerged. Such advances in understanding plant mechanoresponsive development have relied heavily on comparison with mechanosensors characterized in organisms such as Saccharomyces cerevisiae and Escherichia coli, but key questions remain about the cellular basis of the plant mechanosensory system.
• Ribosomes in axons – scrounging from the neighbors?
  - Trends Cell Biol 19(5):236-243 (2009)
  Decades of controversy regarding ribosome occurrence in axons are finally coalescing to a realization that the protein synthesis machinery is recruited and activated in both central and peripheral axons during development and in adult peripheral axons upon injury. Exciting recent findings indicate that ribosome recruitment to axons occurs via lateral transfer from glial cells, a mechanism that could be part of a continuum of intercellular communication systems including tunneling nanotubes and exosomes. Such transcellular interactions could have crucial roles in nervous system functions and will provide new avenues for research into long-standing problems.