Name: pemK RNA motif [1]
Symbol: pemK
Found in: organisms within the phylum Bacillota
Comments: pemK motif RNAs likely function as cis-regulatory elements, in view of their positions upstream of protein-coding genes. Indeed, the RNAs are upstream of multiple genes that encode non-homologous proteins. If all examples of the RNA were upstream of homologous genes, there is the possibility that the RNAs were conserved in that position simply by inheritance. The non-homology of the genes downstream of pemK RNAs makes this scenario less likely.
cis-regulatory RNAs such as riboswitches in Bacillota are often followed by Rho-independent transcription terminators, and they use these transcription terminators as part of a regulatory mechanism. Specifically, depending on the regulatory state of the cis-regulatory RNA, formation of the transcription terminator is either prevented or allowed via alternate secondary structures. pemK RNAs, however, are very rarely followed by a transcription terminator. This fact could raise the possibility that these RNAs are not cis-regulatory, but rather function as small RNAs. However, there are some cis-regulatory RNAs in Bacillota that do not use Rho-independent transcription terminations as a regulatory mechanism, e.g., the yjdF RNA motif.