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N-terminal acetylation shapes protein fate during protein biosynthesis at the ribosome. Here the authors show that the NatA enzyme forms dynamic multi-factor complexes at the ribosome, acting as an interaction hub that coordinates cotranslational protein maturation.

PMTs are fungal O-mannosyltransferases embedded in the ER membrane. Here, structures of the Pmt4 homodimer reveal distinct features of this PMT family and uncover an additional cytosolic binding site for the Dol-P-Man substrate lipid.

How methionine excision and acetylation are co-translationally coordinated at the ribosome has remained elusive. Here, the authors report cryo-EM structures of two different multi-protein assemblies capable of both successive enzymatic functions.

N-terminal acetylation is a common eukaryotic protein modification that is primarily catalysed by the N-acetyl transferase complex A (NatA). Here, the authors present the crystal structure of NatA bound to Huntingtin yeast two-hybrid protein K (HypK) and show that HypK is a negative regulator of NatA.

The yeast ribosome-associated complex (RAC) is formed by Hsp40 protein Zuo1 and the atypical Hsp70 chaperone Ssz1. Structural analyses show Ssz1 in a hybrid conformation between the open and closed state and its substrate-binding domain completed by Zuo1.

Here, the authors use cryo-EM to study cotranslational protein folding by the eukaryotic RAC complex and its conformational dynamics on the 80S ribosome

Newly synthesized secretory and membrane proteins contain cleavable signal sequences at the N terminus that allow for cotranslational protein targeting by interaction with the signal recognition particle (SRP). New results now suggest that signal sequences enable the conserved SRP RNA to accelerate complex formation with the SRP receptor.

Nuclear chromodomain-containing proteins read the epigenetic code by recognizing methylated lysine residues in histone tails. Structural analysis of the cytoplasmic chloroplast signal recognition particle subunit cpSRP34 in complex with the cpSRP54 subunit C-terminal tail comprising an arginine-rich motif reveals that a twinned aromatic cage reads two neighboring nonmethylated arginine residues and adapts chromodomains to a function outside the nucleus.

Here, the authors provide insights into a splicing quality control mechanism. The Gpl1–Gih35 complex binds to the active site of aberrant spliceosomes, blocks splicing progression and triggers the spliceosome discard pathway.

The role of methionine aminopeptidase 2 (MAP2) at the ribosome goes beyond N-terminal methionine excision. Klein et al. use cryo-EM to identify a second MAP2 binding site on the ribosome, and describe the dynamic interactions of MAP2 at the ribosome.

High-resolution cryo-EM structures of a thermophilic 80S ribosome in two rotational states in complex with the protective factor Stm1, eEF2, and nascent chains are presented, providing insights into rRNA modifications and eukaryotic translation.

The human PAXT complex and the MTREC complex in fission yeast are important exosome cofactors, serving in the degradation of specific noncoding RNAs. Here, the authors combine structural, biochemical and in vivo methods to show how Red1 recruits the Mtl1 helicase by an interface not seen before in helicase-adaptor complexes.

Tail-anchored (TA) membrane protein biogenesis is mediated by the GET insertase. Here, authors present cryo-EM and X-ray structures, MD simulations and functional data for human and fungal insertases showing membrane remodeling for TA insertion.

Ribosomes assemble through a process involving about 200 biogenesis factors and series of remodeling steps. Here the authors present the structures of the Rea1-MIDAS domain alone and in complex with its binding partners, shedding light on the process of mechanochemical release of the assembly factors Rsa4 and Ytm1 from the pre-60S particle.

The ribosome-associated complex (RAC), which contains the Hsp40 protein Zuo1 and the non-canonical Hsp70 protein Ssz1 forms a chaperone triad with the fungal-specific Hsp70 protein Ssb. Here the authors combine X-ray crystallography, crosslinking and biochemical experiments and present the structure of the Zuo1 N-terminus bound to Ssz1 and demonstrate that Ssz1 is an active chaperone for nascent chains.

The ErbB3 receptor binding protein Ebp1 binds to ribosomes and is linked to translational control. Here, the authors present the cryo-EM structure of human Ebp1 bound to a non-translating 80S ribosome and find that Ebp1 blocks the tunnel exit and recruits the rRNA expansion segment ES27L to the tunnel exit.

A method called UltraSelex for identifying RNA aptamers has been developed. UltraSelex is noniterative and can combine biochemical partitioning, high-throughput sequencing and computational signal-to-background rank modeling of hits in approximately 1 day.

Here the authors show how the MTREC core protein Red1 binds to and sequesters Pla1 from the 3’-end processing machinery to hyperadenylate cryptic unstable transcripts and target them to the exosome for efficient degradation.

Biogenesis of the 80S ribosome involves more than 200 pre-ribosomal factors, which ensure the sequential assembly of ribosomal proteins and RNAs. Here the authors show that the nuclear transport adaptor Syo1 shields the 5S RNP-docking site on RpL11 before incorporation into the pre-60S through molecular mimicry.

WUSCHEL is a homeodomain transcription factor that is essential for stem cell maintenance in the plant shoot apical meristem. Here, via structural and biochemical approaches, Sloan et al. show that strong WUSCHEL binding to preferential target motifs can be attributed to dimer formation that stabilizes DNA binding.

In yeast, the heterodimeric ribosome-associated complex (RAC) acts in concert with the Hsp70 protein Ssb, forming a unique chaperone triad. Here the authors use structural and biochemical approaches to shed light on how translation and folding are coupled in eukaryotes.

Sec62 is a membrane-bound protein that is involved in the translocation of proteins via the signal recognition particle-independent pathway. Here, the authors show that the receptor SRα displaces Sec62 from the translocon and isolate the domain on SRα that is responsible for this.

The eukaryotic ribosome-associated complex (RAC) chaperone is poorly understood. Structural analyses now provide insight into the catalytic inactivity and possible functions of the Ssz1 subunit and reveal that RAC interacts with the ribosome via the Zuo1 subunit. RAC crouches over the ribosomal exit tunnel, where its conformation may be controlled by the ribosomal expansion segment ES27.

SRP-type GTPases deviate from other GTPases in that they are not activated by GTPase-activating proteins (GAPs). New studies show that the MinD-type protein YlxH activates the SRP-GTPase FlhF, which is involved in flagellar biosynthesis. The crystal structure of the Bacillus subtilis FlhF–effector complex reveals the mechanism of activation, the general concept of which may also apply to RNA-mediated activation of the SRP-GTPases Ffh and FtsY.

The chloroplast signal recognition particle delivers LHCPs to the thylakoid membrane by interaction of cpSRP43 with the Alb3 insertase. Here the authors decipher the specific recognition of the Alb3 C-terminal tail within the interface of two communicating chromodomains by structural biochemistry.

Many proteins must be integrated into or transported across a membrane to reach their site of function. Whereas ATP-dependent factors bind to completed polypeptides and chaperone them until membrane translocation is initiated, a GTP-dependent co-translational pathway couples ongoing protein synthesis to membrane transport.

TRIM21 mediates intracellular antibody immunity and is exploited for targeted protein degradation using Trim-Away technology. Here, the authors dissect the ubiquitination requirements for Trim-Away, providing an explanation for how TRIM21 can target diverse substrates for degradation.

Our understanding of ribosome biogenesis is limited by a lack of structural knowledge of assembly intermediates. Here, Leidig et al.report a high-resolution cryo-EM structure of a pre-60S particle that suggests that substantial rearrangements of the 5S RNP are required during ribosome maturation.

The Braun lab shows that the conserved nuclear membrane protein Lem2 interacts with the MTREC complex of the nuclear-exosome pathway to promote recruitment and degradation of ncRNAs and meiotic transcripts at the nuclear periphery in Schizosaccharomyces pombe.

SIMIBI-type NTP-binding proteins are an ancient subfamily of nucleotide-binding proteins that comprises both dimeric ATPases and GTPases (SIMIBI 'twins'). This Perspective focuses on a subset of SIMIBI proteins with a defined function in protein targeting and localization, and aims to define common mechanistic principles and differences for these proteins.

Crystallographic snapshots illustrate the catalytic cycle and illuminate the mechanism by which the enzyme Pdx1 shuttles intermediates between lysine residues in its two active sites during the biosynthesis of pyridoxal 5′-phosphate.

The synthesis of ribosomes requires the orderly assembly of many proteins and large RNA molecules, a process that involves several assembly factors. Here the authors show that dedicated chaperones capture the N termini of specific nascent ribosomal proteins to promote folding and assembly into maturing ribosomes.

Cryo-EM analysis of a bacterial SRP reveals that, differently from eukaryotic SRP, it interacts with the ribosome via contacts between the 6S RNA and the 23S rRNA to mediate translational slowdown.

Recent structures of eukaryotic membrane protein insertases of the Oxa1 superfamily reveal a conserved protein module and common mechanistic principles that enable membrane insertion of a diverse set of substrates.

The SRP Alu domain is involved in co-translational protein targeting. Soni et al. investigate the Alu domain of Plasmodium falciparum, the agent of malaria, and find that unlike any other it adopts an open conformation.

Layer et al. present a crystal structure of Naa20, the catalytic subunit of an N-terminal acetyltransferase NatB, in complex with its competitive inhibitor CoA-Ac-MDEL. They find that Naa20 alone can acetylate NatB in vitro while Naa25, the auxiliary subunit of Naa20, increases the substrate affinity of Naa20. This study provides insights into the development of NAT inhibitors.

The ribosome-associated complex (RAC) is formed by the JD protein Zuo1 and the unconventional Hsp70 Ssz1. This Review presents recent developments that have increased our understanding of RAC's mechanisms and cellular functions.