Methods to introduce targeted double-strand breaks (DSBs) into DNA enable precise genome editing by increasing the rate at which externally supplied DNA fragments are incorporated into the genome through homologous recombination. The efficiency of these methods is limited by non-homologous end joining (NHEJ), an alternative DNA repair pathway that competes with homology-directed repair (HDR). To promote HDR at the expense of NHEJ, we targeted DNA ligase IV, a key enzyme in the NHEJ pathway, using the inhibitor Scr7. Scr7 treatment increased the efficiency of HDR-mediated genome editing using Cas9 in mammalian cell lines and in mice for all four genes examined up to 19-fold. This approach should be applicable to other customizable endonucleases, such as zinc finger nucleases and transcription activator like effector nucleases, and to non-mammalian cells with sufficiently conserved mechanisms of NHEJ and HDR.

Vascular plants appeared ~410 million years ago then diverged into several lineages of which only two survive: the euphyllophytes (ferns and seed plants) and the lycophytes (1). We report here the genome sequence of the lycophyte Selaginella moellendorffii (Selaginella), the first non-seed vascular plant genome reported. By comparing gene content in evolutionary diverse taxa, we found that the transition from a gametophyte- to sporophyte-dominated life cycle required far fewer new genes than the transition from a non-seed vascular to a flowering plant, while secondary metabolic genes expanded extensively and in parallel in the lycophyte and angiosperm lineages. Selaginella differs in post-transcriptional gene regulation, including small RNA regulation of repetitive elements, an absence of the tasiRNA pathway and extensive RNA editing of organellar genes.

Mutation in Cu/Zn-superoxide dismutase (SOD1) is a cause of familial amyotrophic lateral sclerosis (ALS).[Keywords: Amyotrophic lateral sclerosis; endoplasmic reticulum-associated degradation; endoplasmic reticulum stress; Derlin-1; ASK1] Supplemental material is available at http://www.genesdev.org.

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We developed modified RBCs to serve as carriers for systemic delivery of a wide array of payloads. These RBCs contain modified proteins on their plasma membrane, which can be labeled in a sortase-catalyzed reaction under native conditions without inflicting damage to the target membrane or cell. Sortase accommodates a wide range of natural and synthetic payloads that allow modification of RBCs with substituents that cannot be encoded genetically. 2 with a favorable surface-to-volume ratio; and (vi) the absence of a nucleus, mitochondria, and any DNA. Thus, any modification made to the DNA of RBC precursors is eliminated upon their enucleation and cannot lead to abnormal growth or tumorigenicity after their transfusion into a recipient.Engineered RBCs have been generated using encapsulation (2-4), by noncovalent attachment of foreign peptides, or through installation of proteins by fusion to a monoclonal antibody specific for an RBC surface protein (5, 6).However, modified RBCs have limitations if intended for application in vivo. Encapsulation allows the entrapment of sizable quantities of material but does so at the expense of disrupting plasma membrane integrity, with a concomitant reduction in circulatory half life of the modified RBCs. Osmosis-driven entrapment limits the chemical nature of materials that can be encapsulated successfully, the site of release is difficult to control, and encapsulated enzymes are functional only at the final destination, compromising reusability at other sites (5, 6). Targeting of cargo to RBCs by fusion to an RBC-specific antibody, (e.g., anti-glycophorin antibody), has limitations because this mode of attachment to the RBC is noncovalent and dissociates readily, thus reducing circulatory half life and mass of cargo available for delivery (5, 6). Other developments that exploit RBCs for targeted delivery include nanoparticles enveloped by an RBC-mimicking membrane and RBC-shaped polymers (1). The short in vivo survival rate of these RBC-inspired carriers (∼7 d maximum) may limit their therapeutic utility.There is a need to develop new methodology for engineering RBCs so that they can carry a wide variety of useful cargoes to specific locations in the body. We describe an approach that involves minimal modification of the RBCs, with preservation of plasma membrane integrity. The method involves sortase-mediated site-specific covalent attachment of payloads to specific RBC surface proteins.Bacterial sortases are transpeptidases capable of modifying suitably modified proteins in a covalent and site-specific manner (7,8). Sortase A from Staphylococcus aureus recognizes an LPXTG motif positioned close to the substrate's C terminus and cleaves between T and G to form a covalent acyl-enzyme intermediate. This intermediate is resolved by a nucleophilic N-terminal glycine residue on an appropriately designed probe (9) with concomitant formation of a peptide bond between substrate and probe. Conversely, a protein may be labeled at its N terminus by extending it with suitably exposed g...

Significance Immune-mediated diseases are prevalent, debilitating, and costly. Unfortunately, current treatments rely on nonspecific immunosuppression, which also shuts down a protective immune response. To circumvent this, we exploited the noninflammatory natural means of clearance of red blood cells (RBCs), in combination with sortase-mediated RBC surface modification to display disease-associated autoantigens as RBCs’ own antigens. We found that this strategy holds promise for prophylaxis and therapy, as shown in a mouse model of multiple sclerosis and of type 1 diabetes.

Cells possess ER quality control systems to adapt to ER stress and maintain their function. ER-stress-induced pre-emptive quality control (ER pQC) selectively degrades ER proteins via translocational attenuation during ER stress. However, the molecular mechanism underlying this process remains unclear. Here, we find that most newly synthesized endogenous transthyretin proteins are rerouted to the cytosol without cleavage of the signal peptide, resulting in proteasomal degradation in hepatocytes during ER stress. Derlin family proteins (Derlins), which are ER-associated degradation components, reroute specific ER proteins, but not ER chaperones, from the translocon to the proteasome through interactions with the signal recognition particle (SRP). Moreover, the cytosolic chaperone Bag6 and the AAA-ATPase p97 contribute to the degradation of ER pQC substrates. These findings demonstrate that Derlins-mediated substrate-specific rerouting and Bag6- and p97-mediated effective degradation contribute to the maintenance of ER homeostasis without the need for translocation.

In the multi-cellular community, cells with different properties often compete with each other for survival and space. This process is named cell competition and was originally discovered in Drosophila. Recent studies have revealed that comparable phenomena also occur in mammals under various physiological and pathological conditions. Within the epithelium, normal cells often recognize the presence of the neighboring transformed cells and actively eliminate them from the epithelium; a process termed EDAC (Epithelial Defense Against Cancer). Furthermore, physical force can play a crucial role in the intercellular recognition and elimination of loser cells during cell competition. Further studies are expected to reveal a variety of roles of cell competition in embryonic development and human diseases.