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New structural analyses suggest two different models for poly(ADP-ribose) polymerase 1 (PARP1) activation by single- and double-strand DNA breaks, providing evidence for PARP1 activation in cis and in trans.
RNA silencing is a sequence-specific gene regulation system conserved in eukaryotes, at the core of which lies the Argonaute protein family. Crystallographic studies of eukaryotic Argonaute proteins now reveal remarkably similar overall structures to their prokaryotic homologs while shedding new light on the fundamental relationship between their conformational dynamics and sophisticated strategies to silence specific targets.
Understanding how microRNAs (miRNAs) silence targeted mRNAs has been the focus of intensive research. This Review describes recent advances, with an emphasis on how the miRNA-mediated silencing complex (miRISC) controls gene expression by inhibiting translation and/or mRNA decay, and how trans-acting factors control miRNA action.
Cells have evolved so-called mRNA surveillance mechanisms to monitor mRNAs as they are translated and to degrade troublesome transcripts. Studies of mRNA surveillance have traditionally focused on mRNA fate. In this Perspective, the authors explore mRNA surveillance from the viewpoint of its origins on the ribosome, which should lead to new and unanticipated insights that inform future studies.
Translation initiation requires the formation of a pre-initiation complex that recruits the 5′ end of the mRNA and scans along it to locate the start codon. Genetic, biochemical and structural studies have shed light on the molecular mechanisms underlying the individual steps of this complex process. This Review describes our current understanding of eukaryotic translation initiation and outlines some important outstanding questions in the field.
Recent studies have revealed how poly(A) tail length and the selection of alternative polyadenylation sites contribute to translational control. This Review discusses how mechanisms of alternative polyadenylation, deadenylation and cytoplasmic polyadenylation are coordinated to modulate gene expression in inflammation, learning and memory acquisition, and early development.
The recent X-ray structures of the complete ribosome and large and small subunits from eukaryotes allow these structures to be compared to the previously determined structures of bacterial ribosomes. This Review describes bacterial and eukaryotic ribosomes as a conserved core and two specific shells and focuses on selected bacteria- and eukaryote-specific structural features and their functional implications.
PrPSc, the infective agent for transmissible spongiform encephalopathies, is the misfolded form of the prion protein that can template the conversion of the native fold of the protein (PrPC). The high-resolution structure of PrPSc remains elusive. This review presents recent progress in the area and existing structural models, in addition to discussing the challenges ahead.
Finding biologically relevant targets is a prerequisite for understanding the function of any trans regulator of gene expression, but this can be particularly challenging with microRNAs (miRNAs). A study in this issue addresses the problem by identifying a novel mode of miRNA target recognition.
A complex of PUF (named after founding members Pumilio and Fem-3 binding factor) and Argonaute proteins can stall translation elongation on bound mRNAs by interacting with eEF1A and inhibiting its GTPase activity.
The Cbl family of RING finger ubiquitin ligases regulates signaling in many systems. Two new studies provide a structural basis for how phosphorylation of a specific tyrosine in the Cbl proteins enhances their ubiquitin ligase activity, giving insight into how ubiquitination by Cbl proteins is restricted to specific substrates.
The proteins that 'pump' neurotransmitters into neurons, clearing the synapse after a nerve impulse, are central players in coherent brain function and are targets of many psychotropic drugs. Two groups now endeavor to resolve a fundamental controversy about how these proteins work. The results shed new light on the controversy but do not end it.
Structural studies of the epidermal growth factor receptor (EGFR) have advanced greatly in recent years, but they have used a 'divide-and-conquer' approach for independent study of the intracellular and extracellular regions. Several recent papers provide important new perspectives on 'undivided' EGFR and describe the initial steps in reconstructing signaling behavior of the intact receptor.
Oncogene-induced replication stress and DNA damage are among the hallmarks of cancer. A recent study explores how different levels of replication stress affect animal development and tumorigenesis, and how targeting of the replication stress–signaling pathway of ATR and Chk1 kinases can be exploited for selective killing of cancer cells.
