The ''folE'' RNA motif, now known as the THF-II riboswitch, is a conserved

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

structure that was discovered by bioinformatics. ''folE'' motifs are found in

Alphaproteobacteria ''Alphaproteobacteria'' or ''α-proteobacteria'', also called ''α-Purple bacteria'' in earlier literature, is a class of bacteria in the phylum '' Pseudomonadota'' (formerly "Proteobacteria"). The '' Magnetococcales'' and '' Mariprofundales'' ar ...

. ''folE'' motif RNAs likely function as

cis-regulatory element ''Cis''-regulatory elements (CREs) or ''cis''-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morpho ...

s, in view of their positions upstream of protein-coding

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s. Instances of the ''folE'' RNA motif are often located nearby to the predicted Shine-Dalgarno sequence of the downstream gene. This arrangement is consistent with a model of ''cis''-regulation where the RNA allosterically controls access to the Shine-Dalgarno sequence, thus regulating the gene translationally. All known ''folE'' RNAs are present upstream of genes encoding

GTP cyclohydrolase I GTP cyclohydrolase I (GTPCH) () is a member of the GTP cyclohydrolase family of enzymes. GTPCH is part of the folate and biopterin biosynthesis pathways. It is responsible for the hydrolysis of guanosine triphosphate (GTP) to form 7,8-dihydro ...

, which performs a step in

folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...

metabolism. ''folE'' RNAs have been shown to bind

tetrahydrofolate Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a folic acid derivative. Metabolism In humans, tetrahydrofolic acid is produced from dihydrofolic acid by dihydrofolate reductase. This reaction is inhibited by methotrexate. It is convert ...

and related molecules, leading to their designation as a second structural class of tetrahydrofolate

riboswitch In molecular biology, a riboswitch is a regulatory segment of a messenger RNA molecule that binds a small molecule, resulting in a change in Translation (biology), production of the proteins encoded by the mRNA. Thus, an mRNA that contains a ribo ...

es, called THF-II riboswitches.

References

{{reflist Non-coding RNA