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This Week in Cell: Aug 11, 2010

In Cell this week, investigators in France and the US show that "single-stranded DNA transposition is coupled to host replication." They describe a connection between the transposition of IS608 and ISDra2 — members of the same insertion sequence family — which they suggest "uses obligatory single-stranded DNA intermediates, and the host replication fork." Thus, the authors report, "replication direction through the IS plays a crucial role in excision," in that, replication activity is paramount when the IS strand on top is located on the lagging-strand template.

A collaboration led by investigators at the Broad Institute shows that lincRNA-p21 acts as a repressors in p53-dependent transcriptional responses. Inhibition of lincRNA-p21, the authors demonstrate, "affects the expression of hundreds of gene targets enriched for genes normally repressed by p53," as mediated via its physical association with hnRNP-K. "This interaction is required for proper genomic localization of hnRNP-K at repressed genes and regulation of p53 mediates apoptosis," the authors write.

Investigators at the Beth Israel Deaconess Medical Center and their colleagues at Weill Cornell Medical College show that "Plzf regulates germline progenitor self-renewal by opposing mTORC1." Specifically, the team shows that spermatogonial progenitor cells "lacking Plzf, a transcription factor essential for SPC maintenance, have enhanced mTORC1 activity," which is associated with GDNF inhibition, eventually limiting SPC self-renewal.

Also in the most recent issue of Cell, investigators at the University of California, Los Angeles, and their colleagues show that polynucleotide phosphorylase — PNPASE — regulates RNA import into the mitochondrial matrix. "PNPASE RNA processing and import activities were separable and a mitochondrial RNA targeting signal was isolated that enabled RNA import in a PNPASE-dependent manner," the authors write, suggesting that their data "strongly support an unanticipated role for PNPASE."