I noticed an interesting paper this week that details a new experimental technique applied to human cell lines. The method is capable of measuring the half life of proteins in human cell lines for the first time. We have been looking at Yeast data from the O'Shea lab. The yeast data is pretty comprehensive and all available for download. The yeast work uses an epitope tagged strain. Their work in yeast suggests that protein half life correlates well with transcriptional regulation (in some protein clusters).

The new work in humans uses a method called bleach-chase to achieve quantitative measurements of YFP tagged proteins. Importantly they are able to distinguish between proteins that undergo active degradation and those that are duiluted due to the effects of cell growth. That is when the cell divides no more of that particular protein is produced resulting in an overall lower abundance of the protein in the new daughter cells.

They were able to show that proteins with a long half life are generally regulated through dilution whereas those with short protein half lives are typically regulated by protease activity.