RNA PolII is involved in ribosomal RNA transcriptio

Currently, the accepted mechanism of production of 18S, 5.8S and 25S ribosomal RNA components in yeast, is polycistronic transcription by RNA Polymerase I, followed by processing. We show here that Candida albicans, during nutritional limitations produces some of these molecules in a second way, leaving them resistant to a 5’-phosphate requiring exonuclease digestion, as they have more than one 5’ phosphate. This suggested new transcription. Applying Pol I and Pol II inhibitors BMH-21 and DRB, anti-RNA cap antibody, EIF4F subunit of cap-binding protein, chromatin immune-precipitation and nucleolar immune fluorescent microscopy, we show them to be products of Pol II. We also show that rapamycin inhibition of TOR also leads to their production. Oligo ligation/primer extension shows their 5’ ends to be at the processing sites. This appears to be a system to maintain protein production during nutritional limitation. The mechanism allowing Pol II to produce them remains to be elucidated.