Diverse intrinsic properties shape transcript stability and stabilization in Mycolicibacterium smegmatis

In mycobacteria, regulation of transcript degradation is known to occur in response to environmental stress and to facilitate adaptation. However, the mechanisms underlying this regulation are unknown. Here we sought to gain an understanding of the mechanisms controlling mRNA stability by investigating the transcript properties associated with variance in transcript stability and stress-induced transcript stabilization. We performed transcriptome-wide mRNA degradation profiling of Mycolicibacterium smegmatis in both log phase growth and hypoxia-induced growth arrest. The transcriptome was globally stabilized in response to hypoxia, with all transcripts having longer half-lives, but some having greater degrees of stabilization than others. The transcripts of essential genes were generally stabilized more than those of non-essential genes. We then developed machine learning models that utilized a compendium of transcript properties and enabled us to identify the non-linear collective effect of diverse properties on transcript stability and stabilization. The comparisons of these properties confirmed the association of 5 UTRs with transcript stability, along with other differences between leadered and leaderless transcripts. Our analysis highlighted the protective effect of translation in log phase but not in hypoxia-induced growth arrest. Steady-state transcript abundance had a weak negative association with transcript half-life that was stronger in hypoxia, while coding sequence length showed an unexpected correlation with half-life in hypoxia only. In summary, we found that transcript properties are differentially associated with transcript stability depending on both the transcript type and the growth condition. Our results reveal the complex interplay between transcript features and microenvironment that shapes transcript stability in mycobacteria.