The maintenance of oocytes in the mammalian ovary involves extreme protein longevity.

Women are born with all of their oocytes. The oocyte proteome must be maintained with minimal damage throughout the woman's reproductive life, and hence for decades. Here we report that oocyte and ovarian proteostasis involves extreme protein longevity.

Protein degradation by human 20S proteasomes elucidates the interplay between peptide hydrolysis and splicing.

If and how proteasomes catalyze not only peptide hydrolysis but also peptide splicing is an open question that has divided the scientific community. The debate has so far been based on immunopeptidomics, in vitro digestions of synthetic polypeptides as well as ex vivo and in vivo experiments, which could only indirectly describe proteasome-catalyzed peptide splicing of full-length proteins. Here we develop a workflow-and cognate software - to analyze proteasome-generated non-spliced and spliced peptides produced from entire proteins and apply it to in vitro digestions of 15 proteins, including well-known intrinsically disordered proteins such as human tau and α-Synuclein.

Assessment of treatment options for patients with hepatitis C virus recombinant form 2k/1b.

Aim: Hepatitis C virus (HCV) intergenotype recombinant form (RF) 2k/1b has been actively circulating in HCV-infected patients, and the prevalence of this RF virus in the Republic of Georgia is one of the highest reported worldwide. The aim of this study was to define the optimal treatment regimen for patients with RF_2k/1b.

Methods: We analyzed the data of 2735 patients who started treatment at the Medical Center Mrcheveli within Georgia's hepatitis C elimination program from May 2015 through December 2019.

Analysis of protein-DNA interactions in chromatin by UV induced cross-linking and mass spectrometry.

Protein-DNA interactions are key to the functionality and stability of the genome. Identification and mapping of protein-DNA interaction interfaces and sites is crucial for understanding DNA-dependent processes. Here, we present a workflow that allows mass spectrometric (MS) identification of proteins in direct contact with DNA in reconstituted and native chromatin after cross-linking by ultraviolet (UV) light.

Identification of hepatitis C virus 2k/1b intergenotypic recombinants in Georgia.

Background And Aims: This study aimed to evaluate the prevalence of the hepatitis C virus intergenotype recombinant strain RF1_2k/1b in Georgia, confirm viral recombination by full genome sequencing, and determine a genetic relationship with previously described recombinant hepatitis C viruses.

Methods: We retrospectively analysed data from 1421 Georgian patients with chronic hepatitis C. Genotyping was performed with the INNO-LiPA VERSANT HCV Genotype 2.

Preferential binding of a stable G3BP ribonucleoprotein complex to intron-retaining transcripts in mouse brain and modulation of their expression in the cerebellum.

Neuronal granules play an important role in the localization and transport of translationally silenced messenger ribonucleoproteins in neurons. Among the factors associated with these granules, the RNA-binding protein G3BP1 (stress-granules assembly factor) is involved in neuronal plasticity and is induced in Alzheimer's disease. We immunopurified a stable complex containing G3BP1 from mouse brain and performed high-throughput sequencing and cross-linking immunoprecipitation to identify the associated RNAs.

The polyadenylation complex of Trypanosoma brucei: Characterization of the functional poly(A) polymerase.

The generation of mature mRNA in the protozoan parasite Trypanosoma brucei requires coupled polyadenylation and trans splicing. In contrast to other eukaryotes, we still know very little on components, mechanisms, and dynamics of the 3' end-processing machinery in trypanosomes. To characterize the catalytic core of the polyadenylation complex in T.

Mammalian splicing factor SF1 interacts with SURP domains of U2 snRNP-associated proteins.

Splicing factor 1 (SF1) recognizes the branch point sequence (BPS) at the 3' splice site during the formation of early complex E, thereby pre-bulging the BPS adenosine, thought to facilitate subsequent base-pairing of the U2 snRNA with the BPS. The 65-kDa subunit of U2 snRNP auxiliary factor (U2AF65) interacts with SF1 and was shown to recruit the U2 snRNP to the spliceosome. Co-immunoprecipitation experiments of SF1-interacting proteins from HeLa cell extracts shown here are consistent with the presence of SF1 in early splicing complexes.

Dual tagging as an approach to isolate endogenous chromatin remodeling complexes from Saccharomyces cerevisiae.

Affinity isolation has been an essential technique for molecular studies of cellular assemblies, such as the switch/sucrose non-fermentable (SWI/SNF) family of ATP-dependent chromatin remodeling complexes. However, even biochemically pure isolates can contain heterogeneous mixtures of complexes and their components. In particular, purification strategies that rely on affinity tags fused to only one component of a complex may be susceptible to this phenomenon.

Analyzing the protein assembly and dynamics of the human spliceosome with SILAC.

Quantitative mass spectrometry has become an indispensable tool in proteomic studies. Numerous methods are available and can be applied to approach different issues. In most studies these issues include the quantitative comparison of different cell states, the identification of specific interaction partners or determining degrees of posttranslational modification.

Differential roles of postsynaptic density-93 isoforms in regulating synaptic transmission.

In the postsynaptic density of glutamatergic synapses, the discs large (DLG)-membrane-associated guanylate kinase (MAGUK) family of scaffolding proteins coordinates a multiplicity of signaling pathways to maintain and regulate synaptic transmission. Postsynaptic density-93 (PSD-93) is the most variable paralog in this family; it exists in six different N-terminal isoforms. Probably because of the structural and functional variability of these isoforms, the synaptic role of PSD-93 remains controversial.

An automated in-gel digestion/iTRAQ-labeling workflow for robust quantification of gel-separated proteins.

Simple protein separation by 1DE is a widely used method to reduce sample complexity and to prepare proteins for mass spectrometric identification via in-gel digestion. While several automated solutions are available for in-gel digestion particularly of small cylindric gel plugs derived from 2D gels, the processing of larger 1D gel-derived gel bands with liquid handling work stations is less well established in the field. Here, we introduce a digestion device tailored to this purpose and validate its performance in comparison to manual in-gel digestion.

The cryo-EM structure of the UPF-EJC complex shows UPF1 poised toward the RNA 3' end.

Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance pathway that degrades aberrant mRNAs containing premature termination codons (PTCs). NMD is triggered upon the assembly of the UPF surveillance complex near a PTC. In humans, UPF assembly is prompted by the exon junction complex (EJC).

Phosphorylation site localization in peptides by MALDI MS/MS and the Mascot Delta Score.

Owing to its broad biological significance, the large-scale analysis of protein phosphorylation is more and more getting into the focus of proteomic research. Thousands of phosphopeptides can nowadays be identified using state-of-the-art tandem mass spectrometers in conjunction with sequence database searching, but localizing the phosphate group to a particular amino acid in the peptide sequence is often still difficult. Using 180 individually synthesized phosphopeptides with precisely known phosphorylation sites (p-sites), we have assessed the merits of the Mascot Delta Score (MD score) for the assignment of phosphorylation sites from tandem mass spectra (MS/MS) generated on four different matrix-assisted laser desorption ionization (MALDI) mass spectrometers including tandem time-of-flight (TOF/TOF), quadrupole time-of-flight, and ion trap mass analyzers.

The human Pat1b protein: a novel mRNA deadenylation factor identified by a new immunoprecipitation technique.

The complex of the yeast Lsm1p-7p proteins with Pat1p is an important mRNA decay factor that is involved in translational shutdown of deadenylated mRNAs and thus prepares these mRNAs for degradation. While the Lsm proteins are highly conserved, there is no unique mammalian homolog of Pat1p. To identify proteins that interact with human LSm1, we developed a novel immunoprecipitation technique that yields virtually pure immunocomplexes.

The archaeal Lsm protein binds to small RNAs.

Proteins of the Lsm family, including eukaryotic Sm proteins and bacterial Hfq, are key players in RNA metabolism. Little is known about the archaeal homologues of these proteins. Therefore, we characterized the Lsm protein from the haloarchaeon Haloferax volcanii using in vitro and in vivo approaches.

Two DEAD-box proteins may be part of RNA-dependent high-molecular-mass protein complexes in Arabidopsis mitochondria.

Posttranscriptional processes are important for regulation of gene expression in plant mitochondria. DEAD-box proteins, which form a huge protein family with members from all kingdoms, are fundamental components in virtually all types of processes in RNA metabolism. Two members of this protein family, designated PMH1 and PMH2 (for PUTATIVE MITOCHONDRIAL RNA HELICASE), were analyzed and characterized in mitochondria of Arabidopsis (Arabidopsis thaliana).

Proteomic and functional analysis of Argonaute-containing mRNA-protein complexes in human cells.

Members of the Argonaute (Ago) protein family associate with small RNAs and have important roles in RNA silencing. Here, we analysed Ago1- and Ago2-containing protein complexes in human cells. Separation of Ago-associated messenger ribonucleoproteins (mRNPs) showed that Ago1 and Ago2 reside in three complexes with distinct Dicer and RNA-induced silencing complex activities.

The Methanothermobacter thermautotrophicus ExoIII homologue Mth212 is a DNA uridine endonuclease.

The genome of Methanothermobacter thermautotrophicus, as a hitherto unique case, is apparently devoid of genes coding for general uracil DNA glycosylases, the universal mediators of base excision repair following hydrolytic deamination of DNA cytosine residues. We have now identified protein Mth212, a member of the ExoIII family of nucleases, as a possible initiator of DNA uracil repair in this organism. This enzyme, in addition to bearing all the enzymological hallmarks of an ExoIII homologue, is a DNA uridine endonuclease (U-endo) that nicks double-stranded DNA at the 5'-side of a 2'-d-uridine residue, irrespective of the nature of the opposing nucleotide.