Regulation of polyphosphate glucokinase gene expression through co-transcriptional processing in Mycobacterium tuberculosis H37Rv

Transcription is the process that allows the simultaneous folding of RNA molecules, known as co-transcriptional folding. This folding determines the functional properties of RNA molecules and possibly having a critical role during the synthesis as well. This functioning includes the characterized properties of riboswitches and ribozymes as well, which is significant when the transcription rate is comparable to the cellular environment. This study aims to discover a novel non-coding region that is important in the genetic expression of Mycobacterium tuberculosis. In this work, we identified a novel non-coding element of polyphosphate glucokinase (ppgk) gene that undergoes cleavage activity during the transcriptional process in Mycobacterium tuberculosis. We revealed that cleavage occurs within the nascent RNA, and the resultant cleaved 3RNA fragment carries the Shine-Dalgarno (SD) sequence and expression platform. Site-specific mutations provide a strong correlation between the disruption of cleavage activity and expression of ppgk gene. We concluded that co-transcriptional processing at the noncoding region as the required mechanism for ppgk expression that remains constitutive within the bacterial environment. The underlying reason for ppgk mRNA processing and expression is correlated because the non-coding counterpart adopts a hairpin domain that sequesters ribosomal binding site. Thus, the mRNA processing at the immediate upstream of Shine-Dalgarno sequence is required to prevent this sequestration and subsequent expression as well. This study defines the molecular mechanism that is dependent on the transient but highly active structural features of the nascent RNA.