Multicopy single-stranded DNA

[2] Before the discovery of msDNA in myxobacteria,[3][4] a group of swarming, soil-dwelling bacteria, it was thought that the enzymes known as reverse transcriptases (RT) existed only in eukaryotes and viruses.

[5] Further research discovered similarities between HIV-encoded reverse transcriptase and an open reading frame (ORF) found in the msDNA coding region.

After a DNA fragment coding for the production of msDNA in E. coli was discovered,[8] it was conjectured that bacteriophages might have been responsible for the introduction of the RT gene into E.

Over-expression of msDNA is mutagenic, apparently as a result of titrating out repair proteins by the mismatched base pairs that are typical of their structure.

The sustainability of social assemblies that require significant individual investment of energy is generally dependent on the evolution of allorecognition mechanisms that enable groups to distinguish self versus non-self.

Surprisingly, however, experiments in cell-free systems using purified retron reverse transcriptase indicate that cDNA synthesis is directly primed from the 2'-OH group of the specific internal G residue of the primer RNA.

The catalytic region of eukaryotic reverse transcriptase comprises three domains termed the "fingers", "palm", and "thumb" which hold the double-stranded primer-template in a right-hand grip with the 3'-OH of the primer buried in the active site of the polymerase,[17] a cluster of highly conserved acidic and polar residues situated on the palm between what would be the index and middle fingers.

msDNA from Stigmatella aurantiaca compared with msDNA from the closely related Myxococcus xanthus . The hypervariable domain in the DNA sequence is shaded gray. The highly conserved AGC RNA sequence including the branch G is shaded pink. An RNA cleavage site between precursor and product forms of msDNA is indicated by a red triangle. Redrawn from Dhundale et al. [ 1 ]
Proposed mechanism for the synthesis of msDNA. (A) Folding of the primer-template RNA into a secondary structure allows the 2'-OH group of a specific branching G residue to serve as a primer to initiate cDNA synthesis by the retron reverse transcriptase. (B) Synthesis of cDNA is accompanied by RNase H digestion of the template strand. (C) In the completed msDNA molecule, part of the RNA template remains joined to the 5' end of the cDNA. [ 10 ]