Exported mRNAs are targeted for translation or can undergo degradation by several decay mechanisms. The 533 degradation machinery localizes to cytoplasmic P bodies (PBs). We followed the dynamic properties of PBs in vivo and investigated the mechanism by which PBs scan the cytoplasm. Using proteins of the decapping machinery, we asked whether PBs actively scan the cytoplasm or whether a diffusion-based mechanism is sufficient. Live-cell imaging showed that PBs were anchored mainly to microtubules. Quantitative single-particle tracking demonstrated that most PBs exhibited spatially confined motion dependent on microtubule motion, whereas stationary PB pairs were identified at the centrosome. Some PBs translocated in long-range movements on microtubules. PB mobility was compared with mitochondria, endoplasmic reticulum, peroxisomes, SMN bodies, and stress granules, and diffusion coefficients were calculated. Disruption of the microtubule network caused a significant reduction in PB mobility together with an induction of PB assembly. However, FRAP measurements showed that the dynamic flux of assembled PB components was not affected by such treatments. FRAP analysis showed that the decapping enzyme Dcp2 is a nondynamic PB core protein, whereas Dcp1 proteins continuously exchanged with the cytoplasm. This study reveals the mechanism of PB transport, and it demonstrates how PB assembly and disassembly integrate with the presence of an intact cytoskeleton. INTRODUCTIONGene expression begins with the synthesis of mRNA molecules in the nucleus. After processing events, transcripts are exported to the cytoplasm where they can face several posttranscriptional fates, elicited by a balance between cytoplasmic translation and mRNA degradation pathways. Quality control pathways regulate the degradation of mRNAs and facilitate their sequestration or translational repression (Meyer et al., 2004). In eukaryotes, mRNA degradation typically begins with deadenylation, and then either of two major pathways is used. The exosome protein complex degrades mRNAs in the 3Ј35Ј direction, whereas the 5Ј33Ј direction involves other factors, including a decapping enzyme followed by the Xrn1 exonuclease (Parker and Song, 2004).The removal of the cap structure irreversibly marks the mRNA for degradation. The decapping process is tightly regulated biochemically and spatially. It was first discovered that the Xrn1 nuclease localizes in discrete cytoplasmic foci in eukaryotic cells (Bashkirov et al., 1997). Some years later, a decapping protein termed Dcp2 was found to colocalize in Xrn1-foci (Ingelfinger et al., 2002;Lykke-Andersen, 2002;van Dijk et al., 2002), finally leading to the understanding that both yeast (Sheth and Parker, 2003) and mammalian cells (Cougot et al., 2004) contain discrete areas in which mRNA decapping and 5Ј33Ј degradation can occur (Sheth and Parker, 2006). These cytoplasmic foci are now widely known as P bodies (PBs), and they have been referred to as Dcpbodies, processing bodies, mRNA-decay foci, and GW182 bodies. Since ...
Objective No information exists in the literature regarding the effect of mRNA SARS-CoV-2 vaccine on subsequent IVF cycle attempt. We therefore aim to assess the influence of mRNA SARS-CoV-2 vaccine on IVF treatments. Design An observational study. Setting A tertiary, university-affiliated medical center. Patients and Methods All couples undergoing consecutive ovarian stimulation cycles for IVF before and after receiving mRNA SARS-CoV-2 vaccine, and reached the ovum pick-up (OPU) stage. The stimulation characteristics and embryological variables of couples undergoing IVF treatments after receiving mRNA SARS-CoV-2 vaccine were assessed and compared to their IVF cycles prior to vaccination. Main outcome measures Stimulation characteristics and embryological variables. Results Thirty-six couples resumed IVF treatment 7–85 days after receiving mRNA SARS-CoV-2 vaccine. No in-between cycles differences were observed in ovarian stimulation and embryological variables before and after receiving mRNA SARS-CoV-2 vaccination. Conclusions mRNA SARS-CoV-2 vaccine did not affect patients’ performance or ovarian reserve in their immediate subsequent IVF cycle. Future larger studies with longer follow-up will be needed to validate our observations.
BSTRACTThe 59-to-39 mRNA degradation machinery localizes to cytoplasmic processing bodies (P-bodies), which are non-membranous structures found in all eukaryotes. Although P-body function has been intensively studied in yeast, less is known about their role in mammalian cells, such as whether P-body enzymes are actively engaged in mRNA degradation or whether P-bodies serve as mRNA storage depots, particularly during cellular stress. We examined the fate of mammalian mRNAs in P-bodies during translational stress, and show that mRNAs accumulate within Pbodies during amino acid starvation. The 59 and 39 ends of the transcripts residing in P-bodies could be identified, but poly(A) tails were not detected. Using the MS2 mRNA-tagging system for mRNA visualization in living cells, we found that a stationary mRNA population formed in P-bodies during translational stress, which cleared gradually after the stress was relieved. Dcp2-knockdown experiments showed that there is constant degradation of part of the P-body-associated mRNA population. This analysis demonstrates the dual role of P-bodies as decay sites and storage areas under regular and stress conditions.
Processing bodies (PBs) are non-membranous cytoplasmic structures found in all eukaryotes. Many of their components such as the Dcp1 and Dcp2 proteins are highly conserved. Using live-cell imaging we found that PB structures disassembled as cells prepared for cell division, and then began to reassemble during the late stages of cytokinesis. During the cell cycle and as cells passed through S phase, PB numbers increased. However, there was no memory of PB numbers between mother and daughter cells. Examination of hDcp1a and hDcp1b proteins by electrophoresis in mitotic cell extracts showed a pronounced slower migrating band, which was caused by hyper-phosphorylation of the protein. We found that hDcp1a is a phospho-protein during interphase that becomes hyper-phosphorylated in mitotic cells. Using truncations of hDcp1a we localized the region important for hyper-phosphorylation to the center of the protein. Mutational analysis demonstrated the importance of serine 315 in the hyper-phosphorylation process, while other serine residues tested had a minor affect. Live-cell imaging demonstrated that serine mutations in other regions of the protein affected the dynamics of hDcp1a association with the PB structure. Our work demonstrates the control of PB dynamics during the cell cycle via phosphorylation.
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