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Box C/D guide RNAs are abundant noncoding RNAs that primarily function to direct the 2'-O-methylation of specific nucleotides by base-pairing with substrate RNAs. In archaea, a bipartite C/D RNA assembles with L7Ae, Nop5, and the methyltransferase fibrillarin into a modification enzyme with unique substrate specificity. Here, we determined the crystal(More)
Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are processed by the ribonuclease Dicer from distinct precursors, double-stranded RNA (dsRNA) and hairpin RNAs, respectively, although either may guide RNA silencing via a similar complex. The siRNA pathway is antiviral, whereas an emerging role for miRNAs is in the control of development. Here, we(More)
Cerebral concussion was produced in rats by an iron pendulum hitting the external occipital protuberance. This resulted in loss of consciousness lasting from 3 to 10 minutes with prompt recovery and no focal neurological signs. The energy absorbed by the head at the impact was calculated to be about 1450 gm/cm. Light microscopic survey showed only minor(More)