I have a question. We work with S2 cells, and look at the genes that are upregulated during stress and how they are induced when other genes are knocked out. We measure the relative concentration of the genes via qPCR normalized to rpl. Anyways, a few weeks ago we noticed that certain genes that are only upregulated during ER stress were coming ~6 cycles early in unstressed cells. We thawed out new cells and new media and figured that would eliminate the problem, yet it didn't. I know it's not a bacterial infection, and we are pretty sterile with everything, so I am not sure what could be responsible for the cells being stressed. it's not temp. or sugar depriv, or o2 depriv. Do you have any ideas? or similar experience? Thanks so much. How would I determine if its a viral infection?
thank you