Involved in nucleolar processing of pre-18S ribosomal RNA. Required for the early cleavages at sites A0, A1 and A2 during 18S ribosomal pre-RNA processing. Component of a heterotrimeric complex containing IMP3, IMP4 and MPP10. Interacts with snoRNA U3. Component of the ribosomal small subunit (SSU) processome composed of at least 40 protein subunits and snoRNA U3. Interacts with the SSU processome subunits EMG1, IMP3, IMP4, KRR1, NOC4/UTP19, NOP1, RPS4A, RPS4B, RPS6A, RPS6B, RPS7A, RPS7B, RPS9A, RPS9B, RPS14A, RPS14B, UTP1-UTP18, UTP20-UTP22 and UTP25. Belongs to the MPP10 family.