Rpf2p and Rrs1p are required for the integration of the Rpl5/Rpl11/5S rRNA complex within 90S pre-ribosomal particles and the production of the large ribosomal subunit. Our results suggest that Rpf2p is also involved in pre-rRNA synthesis by RNA pol I and could thus contribute to connecting pre-rRNA synthesis to pre-ribosome assembly. We are investigating how Rpf2p interacts with rDNA, pre-rRNA and RNA pol I and whether other early associating components of 90S particles required for large ribosomal subunit synthesis also contribute to RNA pol I transcription.