| Range |
when protein synthesis was blocked ~20min: otherwise ~7hours
|
| Organism |
Mouse Mus musculus |
| Reference |
Heinzel et al., A Myc-dependent division timer complements a cell-death timer to regulate T cell and B cell responses. Nat Immunol. 2017 Jan18(1):96-103. doi: 10.1038/ni.3598. p.99 right column bottom paragraph & p.100 left column top paragraphPubMed ID27820810
|
| Method |
P.99 right column bottom paragraph: "A possible cause for the loss of Myc over time was an increased protein-degradation rate. However, the similarity in decay rates observed for the various stimulation conditions indicated that Myc degradation was constant over time and that a change in the rate of production of Myc was, therefore, the dominant control mechanism. To test this conclusion, [investigators] used cycloheximide to block new protein synthesis. [They] added cycloheximide to Bcl2l11−/− OT-I CD8+ T cells stimulated with N4 peptide, with or without anti-CD28 or IL-2, at several time points and measured Myc protein for a further 6 h. As reported for other systems [ref 18], when protein synthesis was blocked, the half-life of the Myc protein was around 20 min in all stimulation conditions and was independent of whether the amount of Myc in the cycloheximide-free cultures continuing to increase (i.e., cultures treated with anti-CD28 and IL-2, assessed at 18 h) or had plateaued (i.e., cultures treated with N4 peptide only, assessed at 18 h) (Fig. 4d and Supplementary Table 1)." |
| Comments |
P.99 right column bottom paragraph: "[Investigators] found that the half-life of Myc remained relatively stable over time and did not diminish at later time points. Additionally, the rates for Myc production and its degradation were similar in cells of different generations at the same time point (Supplementary Fig. 3d). Thus, the difference of the half-life of the total amount of Myc of ~7 h observed in the culture, relative to the half-life of Myc of 20 min, would mean that the net amounts of Myc observed over time were a result of substantial ongoing production. Therefore, as Myc degradation was not affected by stimulation, time or division, [they] concluded that the loss of Myc protein observed must have been a function of changes in production rates over time. Together these data indicated how Myc levels could be unaffected by cell division (Fig. 1j–o). In contrast to a slow turnover rate, which would result in division-based dilution of the protein (Fig. 1a), the rapid turnover of Myc protein meant that a dynamic equilibrium, balancing production and degradation, was established. As such rates are inherited with division, equilibrium would be reinstated quickly after cell division. Thus, 'timed' changes that reduced the rate of production, leading to eventual division cessation (Fig. 1b), must have been transferred and replicated through cell divisions." |
| Entered by |
Uri M |
| ID |
113421 |