Post-transcriptional regulation of the xynA expression by a novel mRNA binding protein, XaiF

XaiF, a novel 32 kDa protein encoded by the ORF located in the immediate downstream of the xynA gene of Bacillus stearothermophilus No. 236, was identified to be the xylanase-specific trans-activator. In this study, the positive effect of XaiF was confirmed to be xylanase-specific, and the results from Northern blot and in vitro transcription assays showed that the XaiF increased the xynA transcripts at post-transcriptional step. Moreover, analysis of the mRNA decay rate led to the assertion that the XaiF functions to stabilize the xynA mRNA. Intriguingly, in vitro RNA–protein binding assay and analysis using gst-xynA 3′-UTR chimeric gene constructs demonstrated that the XaiF stabilizes xynA mRNA by direct binding onto the 3′-UTR of the mRNA.