Homing of a bacterial group II intron with an intron-encoded protein lacking a recognizable endonuclease domain

Abstract

Rmlnt1 is a functional group II intron found in Sinorhizobium meliloti where it interrupts a group of IS elements of the IS630Tc1 family. In contrast to many other group II introns, the intron-encoded protein (IEP) of Rmlnt1 lacks the characteristic consented part of the Zn domain associated with the IEP endonuclease activity. Nevertheless, in this study, we show that Rmlnt1 is capable of inserting into a vector containing the DNA spanning the Rmlnt1 target site from the genome of S. meliloti. Efficient homing was also observed In the absence of homologous recombination (RecA strains). In addition, it is shown that Rmlnt1 is able to move to its target in a heterologous host (S. medicae). Homing of Rmlnt1 occurs very efficiently upon DNA target uptake (conjugation/electroporation) by the host cell resulting in a proportion of invaded target of 11-30%. Afterwards, the remaining intronless target DNA is protected from intron invasion.