Involved in the 18S rRNA synthesis. Required for the early cleavages at sites A0, A1 and A2. Interacts with KRR1, NOP1, NSR1, PUF6 and UTP22, proteins involved in 18S rRNA synthesis. Interacts also with ribosomal proteins RPS1, RPS3, RPS4, RPS6, RPS11, RPL2, RPL3, RPL4, RPL7, RPL10, RPL20 and RPP0 as well as with the snoRNAs U3 and U14. Present with 656 molecules/cell in log phase SD medium. Belongs to the ESF1 family.