Autoregulation of RNA helicase operon expression

Abstract

The cyanobacterium Synechocystis sp. PCC 6803 encodes for an RNA helicase, crhR, whose expression is regulated by the redox status of the electron transport chain and further enhanced by temperature downshift. In this study, the effect of crhR inactivation was investigated in response to temperature alteration. The inactivation of CrhR has drastic morphological and physiological effects particularly under cold stress, including a rapid cessation of photosynthesis, impaired cell growth, decrease in viability, cell size and DNA content and accumulation of structural abnormalities. Extensive transcript and protein analyses between wild type and mutant cells revealed that CrhR activity is linked to its autoregulation of expression involving complex network acting at the transcriptional and post-transcriptional levels. Furthermore, autoregulation is extended to the rimO-crhR operon where processing and degradation contributes to differential accumulation of the cistrons. Lastly, the potential association of CrhR in a degradosome-polysome complex in the thylakoid membrane is proposed.