Helicases are proteins that use the energy of ATP to unwind nucleic acids and to remodel protein-nucleic acid complexes. They are involved in almost every aspect of the DNA and RNA metabolisms and participate in numerous repair mechanisms that maintain cellular integrity. Helicases are classified into 6 superfamilies (SF1-6). The archaeal Lhr-type proteins are SF2 helicases that are mostly uncharacterized. They have been proposed to be a DNA helicase that acts in DNA recombination and repair processes in Sulfolobales and Methanothermobacter. In parallel, a protein annotated as an Lhr2 protein was also found in the network of proteins involved in RNA metabolism in Thermococcales. To this respect, we performed in-depth phylogenomic analyses to report the classification and taxonomic distribution of Lhr-type proteins in Archaea, and to better understand their relationship with bacterial Lhr. Furthermore, with the goal of envisioning the role(s) of aLhr2 in archaeal cells, we deciphered the enzymatic activities of aLhr2 from Thermococcus barophilus (Tbar). We showed that Tbar-aLhr2 is a DNA/RNA helicase acting on DNA:RNA and RNA:RNA duplexes and proposed that aLhr2 helicases are involved in processes dependent of DNA and RNA transactions.

DNA - the repository of genetic information harbours sequences rich in Guanine that adopt non-B form four-stranded DNA secondary structures termed as G-quadruplexes (G4s). Such non-canonical structures tend to impede the progression of routine replisome and are implicated to have crucial roles in replication, transcription and epigenetic regulation while also ensuring genomic stability. It is now fully established that G4s are enzymatically unfolded by helicases, thus, preventing transient yet apparent impediments to the vital replisome progression. This unfolding of G-quadruplex ensures genetic and epigenetic stability. Given the importance of G4 biology for multiple human parasites such as, Mycobacterium tuberculosis, research efforts probing parasitic G4 biology is gaining momentum with the hope to enable therapeutic intervention. We herein shed light on G4s, conditions that lead to their formation and the mechanisms employed by cells to cause their unfolding. Towards the end, potential drug discovery avenues that arise from targeting parasitic helicases and G4 biology are summarized.