Rbin-1 is a triazinoindole inhibitor of midasin (mdn1), an essential protein for eukaryotic ribosome biogenesis. It inhibits the growth of fission yeast strains in vitro (GI50 = 136 nM) and inhibits mdn1 ATPase activity by approximately 40% when used at a concentration of 1 μM. Rbin-1 inhibits pre-rRNA processing and nuclear export of the pre-60S ribosome subunit in mdn1-ts, but not mdn1-F1093L mutant, S. pombe cells. It also decreases ribosome assembly protein 4 (Rsa4) levels in Rix1 particles, a ribosome assembly intermediate, Rix1-bound Ytm1 levels, and Rix7 and Ppp1 levels in the nucleolar pre-60S particle Nsa1 in mdn1-ts fission yeast cells.
