GTPase required for the synthesis of 40S ribosomal subunits and for processing of pre-ribosomal RNA (pre-rRNA) at sites A0, A1, and A2. Controls access of pre-rRNA intermediates to RCL1 during ribosome biogenesis by binding RCL1 in a GTP-dependent manner, and delivering it to pre-ribosomes. GTP-binding and/or GTP hydrolysis may induce conformational rearrangements within the BMS1-RCL1 complex allowing the interaction of RCL1 with its RNA substrate. Required for RCL1 import into the nucleus. . This is the function of ENSG00000165733 (BMS1, BMS1 ribosome biogenesis factor).