Chromosomal DNA transfer in Mycobacterium smegmatis is mechanistically different from classical Hfr chromosomal DNA transfer.

Classical conjugal DNA transfer of chromosomal DNA in bacteria requires the presence of a cis-acting site, oriT, in the chromosome. Acquisition of an oriT occurs if a conjugative plasmid integrates into the chromosome to form an Hfr donor strain, which can transfer extensive regions of chromosomal DNA. Because oriT sequences are unique, and because transfer occurs in a 5' to 3' direction, the frequency with which a particular gene is inherited by the recipient depends on the gene's location: those closest to the 3' side of oriT are transferred most efficiently.

The RD1 virulence locus of Mycobacterium tuberculosis regulates DNA transfer in Mycobacterium smegmatis.

Conjugal DNA transfer occurs by an atypical mechanism in Mycobacterium smegmatis. The transfer system is chromosomally encoded and requires recipient recombination functions for both chromosome and plasmid transfer. Cis-acting sequences have been identified that confer mobility on nontransferable plasmids, but these are larger and have different properties to canonical oriT sites found in bacterial plasmids.

Characterization of homing endonucleases.

Homing endonucleases are a class of site-specific DNA endonucleases encoded by open reading frames within introns and inteins. They initiate the mobility of their host element by recognizing intronless or inteinless alleles of their host gene and making a double-strand break. The homing endonucleases are notable for their long target sites and a tolerance for sequence polymorphisms in their substrates.

Catalytic domain structure and hypothesis for function of GIY-YIG intron endonuclease I-TevI.

I-TevI, a member of the GIY-YIG family of homing endonucleases, consists of an N-terminal catalytic domain and a C-terminal DNA-binding domain joined by a flexible linker. The GIY-YIG motif is in the N-terminal domain of I-TevI, which corresponds to a phylogenetically widespread catalytic cartridge that is often associated with mobile genetic elements. The crystal structure of the catalytic domain of I-TevI, the first of any GIY-YIG endonuclease, reveals a novel alpha/beta-fold with a central three-stranded antiparallel beta-sheet flanked by three helices.