In the field of molecular biology the 6S RNA is a non-coding RNA that was one of the first to be identified and sequenced. What it does in the bacterial cell was unknown until recently. In the early 2000s scientists found out the function of 6S RNA to be as a regulator of sigma 70-dependent gene transcription. All bacterial RNA polymerases have a subunit called a sigma factor. The sigma factors are important because they control how DNA promoter binding and RNA transcription start sites. Sigma 70 was the first one to be discovered in Escherichia coli. Structure The structure of 6S RNA was defined in 1971. It is a small RNA strand consisting of 184 nucleotides. 6S RNA is a long double-stranded structure and has a single strand loop. The structure is similar to an open promoter complex of DNA structure. Various analyses discovered that 6S RNAs are capable of forming a secondary structure. The secondary structure consists of two irregular helical stem regions, making a large core loop which is called a central knot. Function and Regulation The function of 6S RNA is to regulate transcription for E. coli cell survival because it is essential in the process. 6S RNA specifically associates with RNA polymerase holoenzyme containing the sigma70 specificity factor. This interaction represses expression from sigma70-dependent promoters during stationary phase. Which will lead to activate the transcription from sigma 70 dependent promoters. Therefore, during the change in E. coli from logarithmic growth to stationary phase, the 6S RNA performs as a regulator of transcription. 6S RNA homologs have recently been identified in most bacterial genomes. Polymerase holoenzyme, which contains the housekeeping sigma factor and it can be expressed during different stages of growth. In many Pseudomonadota, 6S RNA may be processed from a transcript encoding homologs of the E. coli YgfA protein, which is a putative methenyltetrahydrofolate synthetase. Diverged 6S RNAs have been identified in additional bacterial lineages. The purD RNA motif has been experimentally shown to overlap with 6S RNA. One way to examine if the activity of 6S RNA by doing a knockout of 6S RNA. Strains with mutations in 6S RNA have a reduction of lifespan in contrast to the wild-type cells after more than 20 days of nonstop culture. When mutant 6S cells cultured with wild-type cells, it will be at a modest disadvantage in the following days of growth. Summary The recently