Retron

A retron is a distinct

Sequence and structure

Retron elements are about 2 kb long. They contain a single operon controlling the synthesis of an RNA transcript carrying three loci, msr, msd, and ret, that are involved in msDNA synthesis. The DNA portion of msDNA is encoded by the msd gene, the RNA portion is encoded by the msr gene, while the product of the ret gene is a reverse transcriptase similar to the RTs produced by retroviruses and other types of retroelements.^[1] Like other reverse transcriptases, the retron RT contains seven regions of conserved amino acids (labeled 1–7 in the figure), including a highly conserved tyr-ala-asp-asp (YADD) sequence associated with the catalytic core. The ret gene product is responsible for processing the msd/msr portion of the RNA transcript into msDNA.

Classification and occurrence

For many years after their discovery in animal viruses, reverse transcriptases were believed to be absent from

• Retrons were the first family of retroelement discovered in bacteria; the other two families of known bacterial retroelements are:
• ribonucleoprotein comprising an intron lariat bound to two intron-coded proteins.^[2]
• diversity-generating retroelements (DGRs).^[3] The DGRs are not mobile, but function to diversify DNA sequences.^[2] For example, DGRs mediate the switch between pathogenic and free-living phases of Bordetella.^[4]

Function

Since retrons are not mobile, their appearance in diverse bacterial species is not a "

Retrons are being developed into genome-editing tools.^[7]

References