Shiftless Is a Novel Member of the Ribosome Stress Surveillance Machinery That Has Evolved to Play a Role in Innate Immunity and Cancer Surveillance.

A longstanding paradox in molecular biology has centered on the question of how very long proteins are synthesized, despite numerous measurements indicating that ribosomes spontaneously shift reading frame at rates that should preclude their ability completely translate their mRNAs. Shiftless (SFL; C19orf66) was originally identified as an interferon responsive gene encoding an antiviral protein, indicating that it is part of the innate immune response. This activity is due to its ability to bind ribosomes that have been programmed by viral sequence elements to shift reading frame. Curiously, Shiftless is constitutively expressed at low levels in mammalian cells. This study examines the effects of altering Shiftless homeostasis, revealing how it may be used by higher eukaryotes to identify and remove spontaneously frameshifted ribosomes, resolving the apparent limitation on protein length. Data also indicate that Shiftless plays a novel role in the ribosome-associated quality control program. A model is proposed wherein SFL recognizes and arrests frameshifted ribosomes, and depending on SFL protein concentrations, either leads to removal of frameshifted ribosomes while leaving mRNAs intact, or to mRNA degradation. We propose that SFL be added to the growing pantheon of proteins involved in surveilling translational fidelity and controlling gene expression in higher eukaryotes.

A Proteomics Survey of Junín Virus Interactions with Human Proteins Reveals Host Factors Required for Arenavirus Replication.

Arenaviruses are negative-strand, enveloped RNA viruses that cause significant human disease. In particular, Junín mammarenavirus (JUNV) is the etiologic agent of Argentine hemorrhagic fever. At present, little is known about the cellular proteins that the arenavirus matrix protein (Z) hijacks to accomplish its various functions, including driving the process of virus release. Furthermore, there is little knowledge regarding host proteins incorporated into arenavirus particles and their importance for virion function. To address these deficiencies, we used mass spectrometry to identify human proteins that (i) interact with the JUNV matrix protein inside cells or within virus-like particles (VLPs) and/or (ii) are incorporated into bona fide JUNV strain Candid#1 particles. Bioinformatics analyses revealed that multiple classes of human proteins were overrepresented in the data sets, including ribosomal proteins, Ras superfamily proteins, and endosomal sorting complex required for transport (ESCRT) proteins. Several of these proteins were required for the propagation of JUNV (ADP ribosylation factor 1 [ARF1], ATPase, H+ transporting, lysosomal 38-kDa, V0 subunit d1 [ATP6V0D1], and peroxiredoxin 3 [PRDX3]), lymphocytic choriomeningitis mammarenavirus (LCMV) (Rab5c), or both viruses (ATP synthase, H+ transporting, mitochondrial F1 complex, beta polypeptide [ATP5B] and IMP dehydrogenase 2 [IMPDH2]). Furthermore, we show that the release of infectious JUNV particles, but not LCMV particles, requires a functional ESCRT pathway and that ATP5B and IMPDH2 are required for JUNV budding. In summary, we have provided a large-scale map of host machinery that associates with JUNV and identified key human proteins required for its propagation. This data set provides a resource for the field to guide antiviral target discovery and to better understand the biology of the arenavirus matrix protein and the importance of host proteins for virion function.IMPORTANCE Arenaviruses are deadly human pathogens for which there are no U.S. Food and Drug Administration-approved vaccines and only limited treatment options. Little is known about the host proteins that are incorporated into arenavirus particles or that associate with its multifunctional matrix protein. Using Junín mammarenavirus (JUNV), the causative agent of Argentine hemorrhagic fever, as a model organism, we mapped the human proteins that are incorporated into JUNV particles or that associate with the JUNV matrix protein. Functional analysis revealed host machinery that is required for JUNV propagation, including the cellular ESCRT pathway. This study improves our understanding of critical arenavirus-host interactions and provides a data set that will guide future studies to better understand arenavirus pathogenesis and identify novel host proteins that can be therapeutically targeted.

Lateralising paraumbilical medial row perforators: dangers and pitfalls in DIEP FLAP planning: a systematic review of 1116 DIEP flaps.

BACKGROUND: The DIEP flap remains the gold standard for autologous breast reconstruction. Recently, the 'perforasome concept' has advanced our understanding of DIEP flap physiology and planning. This study highlights a patient sub-population that produces anomalies to the perforasome hypothesis: those with paramedian, paraumbilical perforators. METHODS: Operation notes and pre-operative CT angiograms from 1116 consecutive DIEP flaps were reviewed retrospectively. Patients with paramedian, paraumbilical perforators (n = 153) were contrasted against a control group whose perforators were not paraumbilical (n = 963). Further sub-group analysis was performed within the study group, comparing paraumbilical perforators that held a lateral course within the flap (n = 25) versus those that held a medial course (n = 128). RESULTS: Rates of post-operative DIEP flap partial necrosis was greater in the study population compared with the control group (6.54% vs. 3% p = 0.032). When analysis was made contrasting paraumbilical perforators that held a lateral course in the flap versus perforators that held a median course, flap necrosis was significantly greater in those with a lateral course (24% vs. 3.13%). CONCLUSION: The perforasome concept has improved our understanding of perfusion from perforators in DIEP flaps. However when the umbilicus presents a physical barrier to blood vessel passage resulting in lateralizing paraumbilical medial row perforators it appears an exception to the "perforasome" rule. Our experience suggests that when a paraumbilical perforator is harvested, a hemi-flap is safe but caution should be exercised when further volume is needed from the contralateral side.