SMG proteins license and execute mRNA degradation via nonsense-mediated mRNA decay in human cells

The cell undergoes various processes such as proliferation, differentiation, and intracellular adjustments due to changes of external conditions. For the adaption to these states precise regulation of gene expression is necessary. Nonsense-mediated mRNA decay (NMD) is a translation-dependent quality control mechanism in eukaryotes. Although NMD is best known for degrading transcripts harboring premature termination codons (PTC), NMD was additionally found to regulate gene expression via targeting physiological transcripts. Phosphorylation of the central NMD factors UPF1 via the SMG1:SMG8:SMG9 complex is a key step during NMD initiation. The kinase SMG1, responsible for UPF1 phosphorylation, is proposed to be negatively regulated by the SMG8 C-terminus and SMG9. Upon phosphorylation, the N- and C-terminal tails of UPF1 function as binding platforms for the decay-inducing factors SMG5:SMG7 and SMG6. Subsequently, the SMG7 C-terminus initiates deadenylation via the recruitment of the CCR4-NOT complex, and the endonuclease SMG6 cleaves the transcript in the vicinity of the PTC. While extensive studies were conducted over the last years, the exact biological mechanism remains undisclosed. Therefore, the aim of this thesis was to examine the regulation of the SMG1:SMG8:SMG9 complex and to investigate the connection of the SMG5:SMG7 and SMG6 pathways in human cultured cells. The regulatory function of SMG8 for SMG1 kinase activity was tested via the deletion of the SMG8 C-terminus. However, cells lacking the SMG8 C-terminus resulted in unchanged NMD activity. Furthermore, the depletion of SMG8 and SMG9 led to minor NMD inhibition and unchanged UPF1 phosphorylation, questioning their regulatory role for SMG1. Nevertheless, treatment with the SMG1 inhibitor SMG1i revealed hypersensitivity of SMG8- or SMG9-deleted cells compared to WT cells: Transcriptome-wide analysis showed an enrichment of NMD-annotated transcripts demonstrating that SMG8 and SMG9 contribute to the robustness of the NMD machinery. Degradation via the SMG5:SMG7 and SMG6 pathway was proposed to be redundant and independent. However, the loss of the SMG5:SMG7 led to the inactivation of SMG6, revealing a functional dependence between both pathways. Transcriptome-wide analysis of SMG5:SMG7-depleted cells revealed severe NMD impairment. Interaction studies demonstrated the intact SMG6-UPF1 binding under these conditions, showing that SMG5:SMG7 are crucial for SMG6 activation. Furthermore, complete NMD abolishment resulted in an accumulation of stalled NMD complexes, suggesting that endonucleolytic cleavage is required for the dissociation of the NMD machinery. Taken together, these data provide comprehensive insights into the SMG1:SMG8:SMG9 complex and the interplay between SMG5:SMG7 and SMG6. Furthermore, these data support an improved model, which consists of two consecutive authentication steps to active SMG6 endonucleolytic activity including UPF1 phosphorylation via SMG1:SMG8:SMG9 and recruitment of SMG5:SMG7

Akūta apendicīta neķirurģiska un ķirurģiska ārstēšana bērniem. Pēdējo 5 gadu literatūras apskats

MedicīnaVeselības aprūpeMedicineHealth Care"Ķirurģiskas un ne-ķirurģiskas ārstēšanas metodes bērniem ar akūtu apendicītu. Pēdējo 5 gadu literatūras apskats" Akūts apendicīts ir biežākais "akūta vēdera" iemesls bērnu populācijā. Agrīna apendektomija ilgstoši bija ārstēšanas zelta standarts, kā rezultātā negatīvo apendektomiju skaits bērniem sastādīja vidēji 10-20%. Arvien lielāku nozīmi akūta apendicīta ārstēšanā bērniem un pieaugušajiem iegūst konservatīvas terapijas iespējas. Šī darba mērķis ir izpētīt un salīdzināt esošos datus par akūta apendicīta ķirurģiskas un konservatīvas ārstēšanas rezultātiem, kas atrodami zinātniskajā literatūrā pēdējo 5 gadu laikā. Komplicēts un nekomplicēts apendicīts jāuzskata par divām klīniski atšķirīgām slimībām, kuru precīza atšķiršana ir izaicinājums, kas ne vienmēr ļauj izvēlēties optimālāko terapiju. Literatūrā atrodamie pētījumi atšķiras pēc sava veida, terapijā izmantotajiem antibakteriālajiem līdzekļiem, novērošanas ilguma u.c. parametriem. Šobrīd konservatīva terapija neuzrāda priekšrocības, salīdzinot ar ķirurģisku terapiju, taču konservatīva terapija ir uzskatāma par drošu terapijas alternatīvu bērniem līdz 7 gadu vecumam. Komplicēta apendicīta gadījumā izvēles metode joprojām ir agrīna apendektomija samazināta komplikāciju attīstīšanās riska un veselības aprūpes izdevumu dēļ.“Non-surgical and surgical treatment of acute appendicitis in children. Literature review of the last 5 years.” Acute appendicitis presents the most common cause of acute abdomen in pediatric population. For years early appendectomy was the gold standard. But false appendectomy rates have still been high with 10-20% in children. Over the past years non-surgical management of acute appendicitis in pediatric and adult population gained importance. The purpose of this literature review is to investigate and compare current literature on surgical and non-surgical treatment of acute appendicitis in children of the last 5 years. Complicated and uncomplicated appendicitis must be looked at as 2 different entities. Yet clinical differentiation between complicated and uncomplicated appendicitis is a challenge impeding optimal treatment. Present studies vary in study design, NOM protocols and selection criteria for participants. Currently non-operative management of uncomplicated appendicitis shows no superiority to surgical management although NOM can display a safe alternative in children > 7 years old. Preferred management of complicated appendicitis in children remains early appendectomy due to less complication risk and decreased health care costs

Untersuchungen zur chemischen Zusammensetzung der organischen Komponente des troposphärischen Aerosols : AFS-Abschlußbericht

[no abstract available