Metabolic turnover and dynamics of modified ribonucleosides by 13C labeling

Therapeutic targeting of FUBP3 phase separation by GATA2-AS1 inhibits malate-aspartate shuttle and neuroblastoma progression via modulating SUZ12 activity

Malate-aspartate shuttle (MAS) is essential for maintaining glycolysis and energy metabolism in tumors, while its regulatory mechanisms in neuroblastoma (NB), the commonest extracranial malignancy during childhood, still remain to be elucidated. Herein, by analyzing multi-omics data, GATA binding protein 2 (GATA2) and its antisense RNA 1 (GATA2-AS1) were identified to suppress MAS during NB progression. Mechanistic studies revealed that GATA2 inhibited the transcription of glutamic-oxaloacetic transaminase 2 (GOT2) and malate dehydrogenase 2 (MDH2). As a long non-coding RNA destabilized by RNA binding motif protein 15-mediated N6-methyladenosine methylation, GATA2-AS1 bound with far upstream element binding protein 3 (FUBP3) to repress its liquid-liquid phase separation and interaction with suppressor of zest 12 (SUZ12), resulting in decrease of SUZ12 activity and epigenetic up-regulation of GATA2 and other tumor suppressors. Rescue experiments revealed that GATA2-AS1 inhibited MAS and NB progression via repressing interaction between FUBP3 and SUZ12. Pre-clinically, administration of lentivirus carrying GATA2-AS1 suppressed MAS, aerobic glycolysis, and aggressive behaviors of NB xenografts. Notably, low GATA2-AS1 or GATA2 expression and high FUBP3, SUZ12, GOT2 or MDH2 levels were linked with unfavorable outcome of NB patients. These findings suggest that GATA2-AS1 inhibits FUBP3 phase separation to repress MAS and NB progression via modulating SUZ12 activity.

Protein-Peptide Turnover Profiling reveals the order of PTM addition and removal during protein maturation

Post-translational modifications (PTMs) regulate various aspects of protein function, including degradation. Mass spectrometric methods relying on pulsed metabolic labeling are popular to quantify turnover rates on a proteome-wide scale. Such data have traditionally been interpreted in the context of protein proteolytic stability. Here, we combine theoretical kinetic modeling with experimental pulsed stable isotope labeling of amino acids in cell culture (pSILAC) for the study of protein phosphorylation. We demonstrate that metabolic labeling combined with PTM-specific enrichment does not measure effects of PTMs on protein stability. Rather, it reveals the relative order of PTM addition and removal along a protein's lifetime-a fundamentally different metric. This is due to interconversion of the measured proteoform species. Using this framework, we identify temporal phosphorylation sites on cell cycle-specific factors and protein complex assembly intermediates. Our results thus allow tying PTMs to the age of the modified proteins.