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This Week in PNAS: Dec 22, 2009

In this week's PNAS, Wayne State University researchers report on a way to monitor DNA synthesis at the single base-pair level. By looking at single-molecule Förster resonance energy transfer, researchers led by David Rueda were able to see the incorporation of three nucleotides by the Escherichia coli DNA polymerase I. They then noted that the FRET efficiency drops off and then returns the expected level. "The most compelling [explanation] is that the polymerase has transiently moved about one nucleotide increment further along the template than the next preinsertion site," the authors write.

Italian researchers report that in Xenopus, the genes that direct late progenitor cells to become the biopolar neurons of the neural retina are inhibited by microRNAs. Using expression and functional screens, they found four microRNAs that are expressed in the embryonic retina and that bind to the 3'UTRs of those genes. The researchers "propose a model in which the proliferation rate and the age of a retinal progenitor are linked to each other and determine the progenitor fate through the activity of a set of miRNAs."

French scientists studied the role of endo-siRNAs in heterochromatin formation in Drosophila. They used the Tombusvirus P19 and Flock House virus B2 proteins to inhibit endo-siRNA function. P19, they found, sequestered transposable element-derived endo-siRNAs and B2 worked on the long precursors. "Our findings provide evidence that a nuclear pool of TE-derived endo-siRNAs is involved in heterochromatin formation in somatic tissues in Drosophila," the researchers write.

In the early edition of PNAS, researchers led by Samir Mitragotri synthesized biomaterial particles that mimic the key features of red blood cells. They report that these synthetic particles can carry oxygen and move through capillaries and hypothesize that they could be used to carry drugs and in medical imaging.

The Scan

Billions for Antivirals

The US is putting $3.2 billion toward a program to develop antivirals to treat COVID-19 in its early stages, the Wall Street Journal reports.

NFT of the Web

Tim Berners-Lee, who developed the World Wide Web, is auctioning its original source code as a non-fungible token, Reuters reports.

23andMe on the Nasdaq

23andMe's shares rose more than 20 percent following its merger with a special purpose acquisition company, as GenomeWeb has reported.

Science Papers Present GWAS of Brain Structure, System for Controlled Gene Transfer

In Science this week: genome-wide association study ties variants to white matter stricture in the brain, and more.