Phosphorylation of pICln by the autophagy activating kinase ULK1 regulates snRNP biogenesis and splice activity of the cell

The Impact of p70S6 Kinase-Dependent Phosphorylation of Gemin2 in UsnRNP Biogenesis

“…The SMN complex fulfills a key role in the biogenesis of uridine-rich small nuclear ribonucleoproteins (UsnRNPs), which is a well-organized stepwise mechanism highly regulated via post-translational modifications [24][25][26][27]. Recent research has demonstrated a significant role of kinases from the mTOR pathway in this context [28,29,36]. In our study presented here, we show that p70S6 kinase interacts with the SMN complex via Gemin2 and influences UsnRNP biogenesis via phosphorylation of Gemin2 (Figure 1).…”

“…Still, it is crucial that the role of pICln be discussed, as it is clear that it builds an RNA-free intermediate, the 6S complex, containing the Sm proteins SmD1, D2, E, F, and G. To form a functional UsnRNP, the two Sm proteins B and D3 must replace pICln. This replacement is catalyzed via phosphorylation of an mTOR pathway kinase, ULK1, which enables the transfer of the Sm proteins onto the SMN complex [28,36,37]. The new mechanism of Gemin2 phosphorylation caused by p70S6K identified here may help to explain the regulation of Sm protein transfer within UsnRNP assembly.…”

“…To address the question of the intracellular effect of Gemin2 phosphorylation, cells which inducibly overexpress GFP, GFP-SMN wt, GFP-Gemin2 wt, GFP-Gemin2 A81, GFP-Gemin2 A166, GFP-Gemin2 D81, and GFP-Gemin2 D166 were generated (Figure 4A,B). Size exclusion chromatography pointed out that Gemin2 is distributed in a higher molecular complex as well as in the distinct molecular weight range from 158 kDa to 100 kDa, the same size range as the 6S complex [36]. This suggests that the 6S complex, consisting of pICln and the Sm proteins D1, D2, E, F, and G, might be a kinetic trap involved in the transfer of Sm proteins onto the SMN complex to keep snRNP biogenesis ongoing [24].…”

“…To see whether the overexpression of GFP-Vector control, GFP-Gemin2 wt, and the GFP-Gemin2 phospho-mutants influenced endogenous Gemin2 complex building, S100 extracts of these cell lines were separated with size exclusion chromatography with a Superose 6 column. Via immunoblot analysis, when a pan-specific antibody against Gemin2 was used, it was evident that Gemin2 is distributed in a complex in the higher molecular size range around 2000 kDa and in addition in the distinct lower molecular weight range from 158 kDa to 100 kDa, comigrating with the so-called 6S complex, an RNA-free intermediate consisting of the chaperone protein pICln and the Sm proteins D1, D2, E, F, and G [36].…”

EnsembleDL-ATG: Identifying autophagy proteins by integrating their sequence and evolutionary information using an ensemble deep learning framework

“…The initiation of autophagy involves the creation of a double-membrane vesicle, known as an autophagosome, which engulfs portions of the cytoplasm. This process involves the coordinated action of a group of conserved proteins coded by autophagy-related (ATG) genes, and among them, the Atg1/unc-51-like kinase (ULK) kinase complex is the most advanced part that plays a vital role in initiating autophagosome formation [27] , [28] , [29] . During autophagosome formation, the LC3/Atg8-phosphatidylethanolamine (PE) and the ATG12-ATG15 ubiquitin-like protein conjugation systems, as well as the ATG9/Atg9 cycling system, are crucial components [30] , [31] .…”