Filarial DNA and its interaction with polyamines and antifilarial drugs

The interaction of DNA from filarial parasite Setaria cervi with polyamines was monitored by melting temperature (Tm) profile, condensation and B to Z DNA transition and compared with DNA of Escherichia coli, Micrococcus luteus and calf thymus having different GC content. Polyamines, viz. spermine and spermidine, stabilized the secondary structure of all DNAs as indicated by increase in Tm value. UV absorption studies indicated B to Z DNA transition in the presence of polyamines. The amount of polyamines required for B to Z transition was dependent upon base composition of DNA and charge of the polyamine. Filarial DNA (AT rich) required six times higher concentration of spermine as compared to GC rich DNA for B to Z DNA transition. Spermidine was not effective in causing transition of S. cervi DNA even at Spd:DNA-P ratio of 20. The antifilarial compound suramin significantly decreased melting temperature of filarial DNA as compared to GC rich DNAs of other parasites. Suramin adversely affected condensation and B to Z DNA transition of various DNAs but prior addition of polyamines protected the DNAs from the destabilizing effect of suramin.