Essential for cell growth. Plays a role in assembly of 60S pre-ribosomal particles in the nucleolus. Also required for replication of the M1 double-stranded RNA of the L-A virus. This latter function may reflect an enhanced requirement for free 60S ribosomal particles for the translation of viral mRNAs which lack poly-A tails. Associates with 60S pre-ribosomal particles. Membrane associated. Present with 3730 molecules/cell in log phase SD medium. Extended N-terminus. Extended N-terminus. Extended N-terminus.