I am doing polysome fractionation for stress conditions for mammalian cell. it seems that peaks of 40S and 60S disappear during stress condition compared to control. I am wondering whether all ribosome are struggling with translation since our translation analysis show us there is an increase in translation.
Research shows that heterogeneity in RP composition endows ribosomes with differential selectivity for translating subpools of transcripts, including those controlling metabolism, cell cycle, and development. See Shi, Zhen, Fujii, Kotaro , Kovary, Kyle M., Genuth, Naomi R, Ro, Hannes L, Teruel, Mary N, Barna , Maria 2017. Heterogeneous Ribosomes Preferentially Translate Distinct Subpools of mRNAs Genome-wide. Molecular Cell 67, 71–83 July 6, 2017 ª 2017 Elsevier Inc. http://dx.doi.org/10.1016/j.molcel.2017.05.021
It is a fact that various growth conditions and different cell types (also various human) have much varying levels of 40, 60, 80 and polysome peaks (and give much different input material per cell dish/mL)
Immediately, it seems counter intuitive that stress should cause an increase in translation. Could it be that it is the result of a heavy production of hsp's and the smaller amount of subunits is because a larger proportion of ribosomes/subunits are engaged in translation (maybe if it is early time point in stress)? It could also be that a large part of the ribosomes are stalled on mRNAs due to the stress - then leading to the involvement of the remaining resources (free 40/60S) for translation and thus the disappearing of 40/60S. Finally, could it be Ribophagy degrading the ribosomes (in order for the cell to save/recycle resources) Obviously, the latter two are not in agreement with the observed increase in translation.
It would be interesting to hear: Which cells are you using? What stress are you imposing on the cells? and how long time? and how do you measure increase in translation?
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