Complete identity and expression of StfZ, the -antisense RNA to the mRNA of the cell division gene , in .

Bacteria regulate FtsZ protein levels through transcriptional and translational mechanisms for proper cell division. A -antisense RNA, StfZ, produced from the intergenic region, was proposed to regulate FtsZ level in . However, its structural identity remained unknown. In this study, we determined the complete sequence of StfZ and identified the isoforms and its promoters. We find that under native physiological conditions, StfZ is expressed at a 1:6 ratio of StfZ: mRNA at all growth phases from three promoters as three isoforms of 366, 474, and 552 nt RNAs. Overexpression of StfZ reduces FtsZ protein level, increases cell length, and blocks cell division without affecting the Z mRNA stability. We did not find differential expression of StfZ under the stress conditions of heat shock, cold shock, or oxidative stress, or at any growth phase. These data indicated that the -encoded StfZ antisense RNA to mRNA may be involved in the fine tuning of mRNA levels available for translation as per the growth-phase-specific requirement at all phases of growth and cell division.