In this Issue: Inflammation.

We live in a microbial world and are often confronted with infection and injury. Inflammation, the response that is unleashed to ward off these insults, has long been familiar to us. Indeed, the words that we still use to describe inflammation -redness and swelling with heat and pain -were coined in the first century A.

Mammalian miRNA RISC recruits CAF1 and PABP to affect PABP-dependent deadenylation.

MicroRNAs (miRNAs) inhibit mRNA expression in general by base pairing to the 3'UTR of target mRNAs and consequently inhibiting translation and/or initiating poly(A) tail deadenylation and mRNA destabilization. Here we examine the mechanism and kinetics of miRNA-mediated deadenylation in mouse Krebs-2 ascites extract. We demonstrate that miRNA-mediated mRNA deadenylation occurs subsequent to initial translational inhibition, indicating a two-step mechanism of miRNA action, which serves to consolidate repression.

Protein kinase Ctheta focusing at the cSMAC is a consequence rather than cause of TCR signaling and is dependent on the MEK/ERK pathway.

Correlation between protein kinase Ctheta focusing within the central supramolecular activation cluster (cSMAC) of the immunological synapse and optimal TCR/costimulatory receptor ligation was interpreted to imply that PKCtheta focusing is required for productive signaling. However, this notion has been called into question and competing data suggest that the cSMAC contributes to receptor down-modulation. The observation that PKCtheta focusing at the cSMAC is promoted by CD28 coligation, and also that it occurs late after proximal tyrosine phosphorylation events have been initiated, has led us to investigate an alternative possibility that PKCtheta focusing might be a consequence rather than a cause of productive integrated signaling.

RNA. Introduction.

Two scientists walk into a bar. After a pint and an exchange of pleasantries, one says to the other, "Where do you come from? Scientifically, I mean." The queried scientist responds, "Out of the RNA world.

A role for the P-body component GW182 in microRNA function.

In animals, the majority of microRNAs regulate gene expression through the RNA interference (RNAi) machinery without inducing small-interfering RNA (siRNA)-directed mRNA cleavage. Thus, the mechanisms by which microRNAs repress their targets have remained elusive. Recently, Argonaute proteins, which are key RNAi effector components, and their target mRNAs were shown to localize to cytoplasmic foci known as P-bodies or GW-bodies.

Purified Argonaute2 and an siRNA form recombinant human RISC.

Genetic, biochemical and structural studies have implicated Argonaute proteins as the catalytic core of the RNAi effector complex, RISC. Here we show that recombinant, human Argonaute2 can combine with a small interfering RNA (siRNA) to form minimal RISC that accurately cleaves substrate RNAs. Recombinant RISC shows many of the properties of RISC purified from human or Drosophila melanogaster cells but also has surprising features.

RNA-interference-based functional genomics in mammalian cells: reverse genetics coming of age.

Sequencing of complete genomes has provided researchers with a wealth of information to study genome organization, genetic instability, and polymorphisms, as well as a knowledge of all potentially expressed genes. The identification of all genes encoded in the human genome opens the door for large-scale systematic gene silencing using small interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs). With the recent development of siRNA and shRNA expression libraries, the application of RNAi technology to assign function to cancer genes and to delineate molecular pathways in which these genes affect in normal and transformed cells, will contribute significantly to the knowledge necessary to develop new and also improve existing cancer therapy.

Argonaute2 is the catalytic engine of mammalian RNAi.

Gene silencing through RNA interference (RNAi) is carried out by RISC, the RNA-induced silencing complex. RISC contains two signature components, small interfering RNAs (siRNAs) and Argonaute family proteins. Here, we show that the multiple Argonaute proteins present in mammals are both biologically and biochemically distinct, with a single mammalian family member, Argonaute2, being responsible for messenger RNA cleavage activity.

Actin cytoskeleton regulates calcium dynamics and NFAT nuclear duration.

T-cell activation by antigen-presenting cells is accompanied by actin polymerization, T-cell receptor (TCR) capping, and formation of the immunological synapse. However, whether actin-dependent events are required for T-cell function is poorly understood. Herein, we provide evidence for an unexpected negative regulatory role of the actin cytoskeleton on TCR-induced cytokine production.

Differential Ras signaling via the antigen receptor and IL-2 receptor in primary T lymphocytes.

Ras can become activated via multiple distinct receptors in T lymphocytes. However, mechanistic studies of Ras signaling in normal T cells have been hampered by the lack of an efficient technology for gene transfer into resting post-thymic cells. We have overcome this limitation by utilizing adenoviral transduction of T cells from Coxsackie/adenovirus receptor transgenic mice.

Gene array and protein expression profiles suggest post-transcriptional regulation during CD8+ T cell differentiation.

Peripheral CD8(+) T cells circulate in a quiescent naive state until they are primed by specific antigen and differentiate into effector cells. In the effector state, CD8(+) T cells acquire cytolytic activity and produce increased levels of cytokines such as interferon-gamma. They also exhibit increased T cell receptor sensitivity, decreased CD28 dependence, and become inhibitable by CTLA-4 and other negative regulatory pathways.