The U3 small nucleolar ribonucleoprotein functions in the first step of preribosomal RNA processing.

@article{Kass1990TheUS,
  title={The U3 small nucleolar ribonucleoprotein functions in the first step of preribosomal RNA processing.},
  author={Susan Kass and K. Tyc and J. A. Steitz and Barbara Sollner-Webb},
  journal={Cell},
  year={1990},
  volume={60 6},
  pages={897-908}
}
The first cleavage in mammalian pre-rRNA maturation occurs near the 5' end within the 5' external transcribed spacer. Using mouse cell extracts, we show that this processing is abolished by micrococcal nuclease pretreatment. Autoantibodies that recognize the U3, U8, and U13 snRNPs (anti-fibrillarin) deplete processing activity from the extract and selectively immunoprecipitate both rRNA substrates and processing products from the reaction. Specific involvement of the U3 snRNP is demonstrated by… CONTINUE READING