The function of ENSG00000120158 (RCL1, RNA terminal phosphate cyclase like 1) is as follows. As part of the small subunit (SSU) processome, it plays a role in 40S-ribosomal-subunit biogenesis in the early pre-rRNA processing steps at sites A0, A1 and A2 that are required for proper maturation of the 18S RNA (By similarity). Activates BMS1 by promoting GDP/GTP exchange (By similarity). Does not have cyclase activity (By similarity). .