The structural characteristics and the substrate recognition properties of RNase ZS1

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(L40)1 mRNA with cloverleaf-like structure was higher than that of pre-tRNA-AspAUC9 and Ub(L40)4 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).

Automated summary

RNase Z(S1) is a key protein involved in regulating gene expression in rice, with its activity depending on the structural characteristics of RNA and not being inhibited by specific RNA sequences.