One of the oldest questions in RNA science is the role of nucleotide modification. Here, the importance of pseudouridine formation (Psi) in the peptidyl transferase center of rRNA was examined by depleting yeast cells of 1-5 snoRNAs that guide a total of six Psi modifications. Translation was impaired substantially with loss of a conserved Psi in the A site of tRNA binding. Depletion of other Psis had subtle or no apparent effect on activity; however, synergistic effects were observed in some combinations. Pseudouridines are proposed to enhance ribosome activity by altering rRNA folding and interactions, with some Psis having greater effects than others. The possibility that modifying snoRNPs might affect ribosome structure in other ways is also discussed.

The activation of NF-B by T-cell receptor (TCR) signaling is critical for T-cell activation during the adaptive immune response. CARD11 is a multidomain adapter that is required for TCR signaling to the IB kinase (IKK) complex. During TCR signaling, the region in CARD11 between the coiled-coil and PDZ domains is phosphorylated by protein kinase C (PKC) in a required step in NF-B activation. In this report, we demonstrate that this region functions as an inhibitory domain (ID) that controls the association of CARD11 with multiple signaling cofactors, including Bcl10, TRAF6, TAK1, IKK␥, and caspase-8, through an interaction that requires both the caspase recruitment domain (CARD) and the coiled-coil domain. Consistent with the ID-mediated control of their association, we demonstrate that TRAF6 and caspase-8 associate with CARD11 in T cells in a signal-inducible manner. Using an RNA interference rescue assay, we demonstrate that the CARD, linker 1, coiled-coil, linker 3, SH3, linker 4, and GUK domains are each required for TCR signaling to NF-B downstream of ID neutralization. Requirements for the CARD, linker 1, and coiled-coil domains in signaling are consistent with their roles in the association of CARD11 with Bcl10, TRAF6, TAK1, caspase-8, and IKK␥. Using Bcl10-and MALT1-deficient cells, we show that CARD11 can recruit signaling cofactors independently of one another in a signal-inducible manner.The NF-B family of transcription factors plays important pleiotropic roles in the regulation of cellular activation, proliferation, and survival. The precise regulation of NF-B activity is critical for several biological processes including innate and adaptive immunity (22, 54), learning and memory (34), epidermal development and homeostasis (2), bone formation and metabolism (65), and embryonic development (19). In most normal cells, NF-B is inactive but is poised for rapid posttranslational activation by a diverse array of stimuli such as bacterial and viral products, proinflammatory cytokines, antigens recognized by lymphocytes, DNA-damaging agents, and UV irradiation.A remarkable aspect of NF-B regulation is that each of these stimuli can activate the IB kinase complex (IKK complex) (50). An emerging theme is that a ligand-receptor pair that may be specialized to a particular biological context will signal to the IKK complex through adapter molecules that can receive stimulusspecific molecular signals and transmit that information to widely expressed signaling cofactors that are of general use. The IKK complex activates NF-B by canonical and noncanonical pathways (50), both of which link IKK kinase activity to the phosphorylation and degradative processing of inhibitory proteins that keep NF-B inactive in the unstimulated state.NF-B is one of the key transcription factors that are induced when a T lymphocyte is activated by antigenic stimulation in the adaptive immune response (51). Following the engagement of antigen by the T-cell receptor (TCR) complex and concomitant triggering of costimulatory receptors like CD...

The regulated activation of NF-κB by antigen receptor signaling is required for normal B and T lymphocyte activation during the adaptive immune response. Dysregulated NF-κB activation is associated with several types of lymphoma, including Diffuse Large B Cell Lymphoma (DLBCL). During normal antigen receptor signaling, the multidomain scaffold protein CARD11 undergoes a transition from a closed, inactive state to an open, active conformation that recruits several signaling proteins into a complex, leading to IKK kinase activation. This transition is regulated by the CARD11 Inhibitory Domain (ID), which participates in intramolecular interactions that prevent cofactor binding to CARD11 prior to signaling, but which is neutralized after receptor engagement by phosphorylation. Several oncogenic CARD11 mutations have been identified in DLBCL that enhance activity and that are mostly found in the Coiled-coil domain. However, the mechanisms by which these mutations cause CARD11 hyperactivity and spontaneous NF-κB activation are poorly understood. In this report, we provide several lines of evidence that oncogenic mutations F123I and L225LI induce CARD11 hyperactivity by disrupting autoinhibition by the CARD11 ID. These mutations disrupt ID-mediated intramolecular interactions, ID-dependent inhibition, and bypass the requirement for ID phosphorylation during T cell receptor signaling. Intriguingly, these mutations selectively enhance the apparent affinity of CARD11 for Bcl10, but not for other signaling proteins that are recruited to CARD11 in an IDdependent manner during normal antigen-receptor signaling. Our results establish a mechanism that explains how DLBCL-associated mutations in CARD11 can initiate spontaneous, receptorindependent activation of NF-κB.The activation of the NF-κB transcription factor by antigen receptor signaling is critical for the proliferation and activation of B and T lymphocytes in the adaptive immune response (1). NF-κB regulates many genes responsible for lymphocyte function, including cytokines, cell surface receptors, and pro-proliferative and anti-apoptotic genes. Mice and humans with mutations that prevent antigen-induced activation of NF-κB fail to mount productive immune responses (2). † This work was supported by RO1AI078980 and PO1AI072677 from the NIH, RSG-06-172-01-LIB from the American Cancer Both T cell receptor (TCR) and B cell receptor (BCR) signaling pathways activate NF-κB through the IKK complex, which is composed of two kinase subunits, IKKα and IKKβ, and a regulatory subunit, IKKγ. The IKK complex phosphorylates IκB proteins that bind and stably retain NF-κB in an inactive state in the cytoplasm. Once phosphorylated, IκB is ubiquitinated and degraded by the 26S proteasome, allowing NF-κB to stably translocate to the nucleus to regulate target genes.The TCR and BCR signaling pathways share many common components that function to activate the IKK complex in a signal-inducible manner. A key scaffold molecule that is required in both pathways is CARD11 (CARMA1, BIMP3...