Mitotic cells: separate but unequal

Mitotic cell divisions, long thought to produce two identical daughter cells, are not entirely equal, according to a new linkurl:study;http://www.pnas.org/cgi/doi/10.1073/pnas.0803027105 published this week in __Proceedings of the National Academy of Sciences__. Proteins destined for degradation are preferentially inherited by one cell over the other, the researchers found. "We hit on an observation that people had missed for 100 years," said linkurl:Eddy De Robertis;http://www.hhmi.ucla.edu/derobertis/ of the University of California, Los Angeles, who led the study. Chromosomes and the mitotic machinery are usually partitioned equally into each new daughter cell during mitosis. Researchers generally assumed this was also true of all other cellular material. But De Robertis and his colleagues now show that for spent proteins, cell division yields an uneven split -- even when dividing cells are bound for the same linkurl:cell fate.;http://www.the-scientist.com/article/display/21075/ De Robertis' team focused on a cell signaling protein called Smad1. After Smad1 is activated, it becomes primed...