DIFFERENTIAL-EFFECTS OF DISTAMYCIN ANALOGS ON AMPLIFICATION OF HUMAN GENE-SEQUENCES BY POLYMERASE-CHAIN REACTION

In this report we analyse the effects of distamycin and five distamyci n analogues on amplification by polymerase-chain reaction (PCR) of two gene sequences displaying a different A+T/G+C content. The first was a 5' region of the human oestrogen receptor (ER) gene, containing a (T A)(26) stretch; the second was a CG-rich sequence of the human Ha-ras oncogene. The results obtained unequivocally demonstrate that the addi tion of one pyrrole ring significantly improves the ability of distamy cin derivatives to interfere with PCR-mediated amplification of the hu man ER genomic region carrying a (TA)(26) stretch. The distamycin anal ogues analysed differ in the number of pyrrole rings and in the presen ce of an N-formyl, an N-formimidoyl or a retroamide group at position X(1). Among compounds carrying the same number of pyrrole rings, those carrying an N-formyl or an N-formimidoyl group retain a similar inhib itory activity. The retroamide analogues, on the contrary, are much le ss efficient in inhibiting PCR-mediated amplification of the 5' ER reg ion. With respect to sequence selectivity both distamycin and distamyc in analogues exhibit a sequence preference, since they do not inhibit PCR amplification of Ha-ras CG-rich gene regions, with the exception o f a distamycin analogue carrying four pyrrole rings.