The structural characteristics and the substrate recognition properties of RNase ZS1

Abstract

TMS5 encodes an RNase Z^S1 protein that can process ubiquitin-60S ribosomal protein L40 family (Ub_L40) mRNAs to regulate thermo-sensitive genic male sterility in rice. Despite the importance of this protein, the structural characteristics and substrate recognition properties of RNase Z^S1 remain unclear. Here, we found that the variations in several conservative amino acids alter the activation of RNase Z^S1, and its recognition of RNA substrates depends on the structure of RNA. RNase Z^S1 acts as a homodimer. The conserved amino acids in or adjacent to enzyme center play a critical role in the enzyme activity of RNase Z^S1 and the conserved amino acids that far from active center have little impact on its enzyme activity. The cleavage efficiency of RNase Z^S1 for pre-tRNA-MetCAU35 and Ub_L401 mRNA with cloverleaf-like structure was higher than that of pre-tRNA-AspAUC9 and Ub_L404 mRNA with imperfect cloverleaf-like structure. This difference implies that the enzyme activity of RNase Z^S1 depends on the cloverleaf-like structure of the RNA. Furthermore, the RNase Z^S1 activity was not inhibited by the 5' leader sequence and 3' CCA motif of pre-tRNA. These findings provide new insights for studying the cleavage characteristics and substrate recognition properties of RNase Z^S.

Keywords: RNase Z; Rice; Thermo-sensitive genic male sterility; Ubiquitin-60S ribosomalprotein L40; tRNA.