RNF14-dependent atypical ubiquitylation promotes translation-coupled resolution of RNA-protein crosslinks.

Reactive aldehydes are abundant endogenous metabolites that challenge homeostasis by crosslinking cellular macromolecules. Aldehyde-induced DNA damage requires repair to prevent cancer and premature aging, but it is unknown whether cells also possess mechanisms that resolve aldehyde-induced RNA lesions. Here, we establish photoactivatable ribonucleoside-enhanced crosslinking (PAR-CL) as a model system to study RNA crosslinking damage in the absence of confounding DNA damage in human cells. We find that such RNA damage causes translation stress by stalling elongating ribosomes, which leads to collisions with trailing ribosomes and activation of multiple stress response pathways. Moreover, we discovered a translation-coupled quality control mechanism that resolves covalent RNA-protein crosslinks. Collisions between translating ribosomes and crosslinked mRNA-binding proteins trigger their modification with atypical K6- and K48-linked ubiquitin chains. Ubiquitylation requires the E3 ligase RNF14 and leads to proteasomal degradation of the protein adduct. Our findings identify RNA lesion-induced translational stress as a central component of crosslinking damage.

TRPV2, a novel player in the human ovary and human granulosa cells.

The cation channel 'transient receptor potential vanilloid 2' (TRPV2) is activated by a broad spectrum of stimuli, including mechanical stretch, endogenous and exogenous chemical compounds, hormones, growth factors, reactive oxygen species, and cannabinoids. TRPV2 is known to be involved in inflammatory and immunological processes, which are also of relevance in the ovary. Yet, neither the presence nor possible roles of TRPV2 in the ovary have been investigated. Data mining indicated expression, for example, in granulosa cells (GCs) of the human ovary in situ, which was retained in cultured GCs derived from patients undergoing medical reproductive procedures. We performed immunohistochemistry of human and rhesus monkey ovarian sections and then cellular studies in cultured GCs, employing the preferential TRPV2 agonist cannabidiol (CBD). Immunohistochemistry showed TRPV2 staining in GCs of large antral follicles and corpus luteum but also in theca, endothelial, and stromal cells. TRPV2 transcript and protein levels increased upon administration of hCG or forskolin. Acutely, application of the agonist CBD elicited transient Ca2+ fluxes, which was followed by the production and secretion of several inflammatory factors, especially COX2, IL6, IL8, and PTX3, in a time- and dose-dependent manner. CBD interfered with progesterone synthesis and altered both the proteome and secretome, as revealed by a proteomic study. While studies are somewhat hampered by the lack of highly specific TRPV2 agonist or antagonists, the results pinpoint TRPV2 as a modulator of inflammation with possible roles in human ovarian (patho-)physiology. Finally, as TRPV2 is activated by cannabinoids, their possible ovarian actions should be further evaluated.

An ovarian phenotype of alpha 7 nicotinic receptor knockout mice.

In brief: Nicotinic acetylcholine receptor alpha 7 (nAChRa7), encoded by Chrna7, is expressed by various murine ovarian cells. Morphological and molecular investigations, including a proteomic study of adult Chrna7 knockout (KO) mouse ovaries, reveal the roles of these receptors in the local regulation of the ovary. Abstract: Nicotinic acetylcholine receptor alpha 7 (nAChRa7), encoded by Chrna7, is involved in cellular functions ranging from synaptic transmission in neurons to regulation of inflammation, cell growth and metabolism to cell death in other cells. Our qPCR results and other studies indicated that nAChRa7 is expressed in the adult mouse ovary, while in situ hybridization and single-cell sequencing data suggested this expression may be shared by several ovarian cells, including fibroblast-like and steroidogenic stroma cells, macrophages and oocytes of small follicles. To explore a possible involvement of nAChRa7 in ovarian functions, we evaluated ovarian morphology of Chrna7-null mutant adult mice (KO) and wildtype mice (WT; 3 months, metestrus) by performing immunohistochemistry, qPCR studies, measurements of serum progesterone and proteomic analyses. The evaluation of serial sections indicated fewer primordial follicles but similar numbers of primary, secondary and tertiary follicles, as well as corpora lutea in KO and WT mice. Atresia was unchanged. Serum progesterone and mRNA levels of proliferation and most apoptosis markers were not changed, yet two typical macrophage markers were elevated. Furthermore, the proteomes of KO ovaries were significantly altered with 96 proteins increased and 32 decreased in abundance in KOs compared to WTs. Among the elevated proteins were markers for stroma cells. Hence, the lack of nAChRa7 causes changes in small follicle counts and alterations of the ovarian stroma cells. The ovarian phenotype of Chrna7 mutant mice links this channel protein to the local regulation of ovarian cells, including stroma cells.

Changes of Protein Expression after CRISPR/Cas9 Knockout of miRNA-142 in Cell Lines Derived from Diffuse Large B-Cell Lymphoma.

BACKGROUND: As microRNA-142 (miR-142) is the only human microRNA gene where mutations have consistently been found in about 20% of all cases of diffuse large B-cell lymphoma (DLBCL), we wanted to determine the impact of miR-142 inactivation on protein expression of DLBCL cell lines. METHODS: miR-142 was deleted by CRISPR/Cas9 knockout in cell lines from DLBCL. RESULTS: By proteome analyses, miR-142 knockout resulted in a consistent up-regulation of 52 but also down-regulation of 41 proteins in GC-DLBCL lines BJAB and SUDHL4. Various mitochondrial ribosomal proteins were up-regulated in line with their pro-tumorigenic properties, while proteins necessary for MHC-I presentation were down-regulated in accordance with the finding that miR-142 knockout mice have a defective immune response. CFL2, CLIC4, STAU1, and TWF1 are known targets of miR-142, and we could additionally confirm AKT1S1, CCNB1, LIMA1, and TFRC as new targets of miR-142-3p or -5p. CONCLUSIONS: Seed-sequence mutants of miR-142 confirmed potential targets and novel targets of miRNAs can be identified in miRNA knockout cell lines. Due to the complex contribution of miRNAs within cellular regulatory networks, in particular when miRNAs highly present in RISC complexes are replaced by other miRNAs, primary effects on gene expression may be covered by secondary layers of regulation.