Directional transport and integration of donor DNA in Haemophilus influenzae transformation.

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Abstract
DNA transport and integration in H. influenzae transformation was studied with a plasmid clone of homologous DNA (p CML6). Donor DNA enters specialized membranous extensions on the cell surface, which are termed transformasomes. Linear DNA undergoes degradation upon exiting transformasomes. DNA without a free end remains within transformasomes and is not degraded. By comparing the fate of label from uniformly labeled vs. middle-labeled DNA, it appears that donor DNA undergoes degradation from an end prior to recombining with the chromosome. Using donor DNA with covalently closed termini (hairpin ends) prevents effcient exit from transformasomes. When 1 hairpin is removed, exit of donor DNA is shown to be directional from the free end, with preferential homologous integration of the 3'' strand for that end.