Role of the 5′-UTR in accumulation of the rbpA1 transcript at low temperature in the cyanobacterium Anabaena variabilis M3

The expression of the rbp genes, which encode RNA-binding proteins with a single RNA-recognition motif and a glycine-rich sequence, is known to increase at low temperature in cyanobacteria. We previously showed that their regulation involved both transcription and mRNA stability. In the present study, various reporter constructs with deletions and mutations were used to analyze this regulation, revealing that at least the following three elements are involved. First, a putative enhancer element is located within the upstream gene. Second, the rbpA1 transcript is dramatically stabilized by a large stem-loop structure located at the 5′ terminus. Third, the transcript is also destabilized by a downstream box located within the coding region.