A Cold Shock-Induced Cyanobacterial RNA Helicase

Abstract

The ability to modify RNA secondary structure is crucial for numerous cellular processes. We have characterized two RNA helicase genes, crhB and crhC, which are differentially expressed in the cyanobacterium Anabaena sp. strain PCC 7120. crhC transcription is limited specifically to cold shock conditions while crhB is expressed under a variety of conditions, including enhanced expression in the cold. This implies that both RNA helicases are involved in the cold acclimation process in cyanobacteria; however, they presumably perform different roles in this adaptation. Although both CrhB and CrhC belong to the DEAD box subfamily of RNA helicases, CrhC encodes a novel RNA helicase, as the highly conserved SAT motif is modified to FAT. This alteration may affect CrhC function and its association with specific RNA targets and/or accessory proteins, interactions required for cold acclimation. Primer extension and analysis of the 5′ untranslated region of crhC revealed the transcriptional start site, as well as a number of putative cold shock-responsive elements. The potential role(s) performed by RNA helicases in the acclimation of cyanobacteria to cold shock is discussed.

Insertional mutagenesis reveals genes involved inBacillus cereusATCC 14579 growth at low temperature

“…The BC0259 product was annotated in the B. cereus ATCC 14579 genome as an RNA helicase with nine motifs that constitute the conserved helicase core and a DEAD box, revealing that it belongs to the DEAD‐box subgroup of the helicase superfamily 2 (Bleichert & Baserga, 2007). RNA helicases participate in many aspects of RNA metabolism (Silverman et al , 2003) and some have been shown to be cold‐induced (Jones et al , 1996; Chamot et al , 1999; Lim et al , 2000). The 9H2 mutant harbours a transpositional insertion upstream of the BC0259 gene, which reduced BC0259 gene expression during adaptation at 10 °C, but not at 30 °C, as revealed by qRT‐PCR experiments.…”

Rearranging RNA structures at 75°C? toward the molecular mechanism and physiological function of the thermus thermophilus DEAD‐box helicase hera

“…Apart from their function at regular growth conditions, a number of DEAD‐box helicases have been identified as cold‐shock proteins, implying a physiological role under stress conditions, among them E. coli CsdA, B. subtilis CshA and CshB, M. burtonii DeaD, and Anabaena ChrC . The expression of E. coli CsdA is induced upon cold‐shock .…”

The role of RNA stability during bacterial stress responses and starvation

“…During the cold shock response, it has been noted for a number of bacteria that the expression of RNA-binding proteins is induced (Sato, 1995;Jones et al, 1996;Chamot et al, 1999). It is tempting to speculate that some of these proteins may function in regulating mRNA stability in response to the shift in growth temperature.…”