GENETICS: RNA Shows Its Sensitive Side
The scientific take on the character of RNA has grown increasingly complex in recent years. Once thought of as a handmaiden to DNA, RNA now appears to be a sophisticated regulator of gene expression. One form of the nucleic acid, microRNA, may regulate a host of vital functions in the cell. A study in the Oct. 5 issue of the journal Cell by (left to right) Changchun Xiao, Klaus Rajewsky, Dinis Pedro Calado, and colleagues, shows that in B cells of the mouse immune system, a particular microRNA (miR-150) specifically targets a certain transcription factor, resulting in finely tuned levels of B cells produced by the mice.

CELL BIOLOGY: Key Found to Proteasome Gate
Though the lock and key metaphor has been used to describe enzyme–substrate interactions for decades, the analogy is almost always a poor fit since enzymes have neither doors nor locks. But a true lock and key may exist in nature. In the Sept. 7 Molecular Cell, HMS researchers led by Alfred Goldberg revealed how a small peptide can pop the cover on the barrel-shaped core proteasome complex. The finding uncovers a crucial step in the degradation of unwanted proteins and may open the door to novel medicines. The work also helps resolve a longstanding biochemical mystery—why ATP is needed for protein degradation in the cell.

PERSONAL GENOMICS: Circle Method Squares with Next-generation Sequencing
PCR works exceptionally well with primers targeting a single piece of DNA, but it doesn’t scale. Gregory Porreca (left), George Church, and their colleagues have developed a new method that allows them to amplify thousands of DNA sequences in a single test tube, bringing affordable genome sequencing within reach. The new method, reported online Oct. 14 in Nature Methods, generates ample material for new, cost-effective sequencers that can read millions of pieces of DNA in an array at the same time.

Copyright 2007 by the President and Fellows of Harvard College