Involved in the small subunit (SSU) processome assembly and function, and in the 18S rRNA synthesis. Required for the early cleavages at sites A0, A1 and A2. Stimulates DBP8 RNA helicase ATPase activity. Component of the 90S pre-ribosomes. Interacts directly with DBP8. Present with 12800 molecules/cell in log phase SD medium. Belongs to the ESF2/ABP1 family.