Required for 40S ribosome biogenesis. Involved in nucleolar processing of pre-18S ribosomal RNA and ribosome assembly. Binds to RNA. Required for female germline development, cell viability during eye development and for survival of dividing cells and epithelial cells during early wing disk development (By similarity). Monomer. Component of the ribosomal small subunit (SSU) processome (By similarity). Belongs to the KRR1 family.