There's a slew of papers in the early online edition of Nature on stem cells. "Five studies show that disabling p53, an essential tumour-suppressor protein, improves the efficiency of stem-cell production," says a News and Views authored in part by Scott Lowe. "Are these results a 'heads up' that cancer cells and stem cells are disturbingly similar?"
Shinya Yamanaka is lead author on one paper that used knockdown, microarray, and functional analysis to show that lack of p53 expression promotes iPS cell generation in human cells, and that the p53-p21 pathway "serves as a barrier not only in tumorigenicity, but also in iPS cell generation." Another paper shows that the Ink4/Arf locus, which encodes three potent tumor suppressors, is a barrier for iPS cell reprogramming. Other exciting work adds more insight.
In this week's issue, more research looks into the chromatin state of embryonic stem cells. In work led by Miguel Ramalho-Santos at UCSF, scientists show that the chromatin remodeling factor Chd1 is required to maintain the open chromatin of pluripotent mouse embryonic stem cells. Down-regulating Chd1 leads to accumulation of heterochromatin, the write, while embryonic stem cells lacking Chd1 are no longer pluripotent. A News and Views article has more.
In Nature Chemical Biology, Caltech scientists have come up with a method to selectively label proteins in specific cells in mixtures of cells. Using non-naturally occurring amino acids that contain azide groups in their side chains, they show that these are only incorporated into proteins in cells that express a mutant of the methionyl-tRNA synthetase enzyme. "When the authors added this amino acid to a co-culture of normal and mutant Escherichia coli cells, only the mutants were subsequently tagged with an alkyne-containing affinity reagent or fluorescent dye," says Andrew Mitchinson in a News and Views piece.
"Biology has just gotten a new set of standards for graphically representing biological information," says a blog post at Scientific Blogging, pointing to a paper published this week in Nature Biotechnology on the new Systems Biology Graphical Notation standard. "SBGN consists of three complementary languages: process diagram, entity relationship diagram and activity flow diagram. Together they enable scientists to represent networks of biochemical interactions in a standard, unambiguous way," the authors, led by The Systems Biology Institute's Hiroaki Kitano and EMBL-EBI's Nicolas Le Novère, say in the abstract.