INVASION OF THE CAG TRIPLET REPEATS BY A COMPLEMENTARY PEPTIDE NUCLEIC-ACID INHIBITS TRANSCRIPTION OF THE ANDROGEN RECEPTOR AND TATA-BINDING PROTEIN GENES AND CORRELATES WITH REFOLDING OF AN ACTIVE NUCLEOSOME CONTAINING A UNIQUE AR GENE SEQUENCE

The DNA sequence of the genes for the androgen receptor (AR) and TATA- binding protein (TBP), like many other genes encoding transcription fa ctors, contains a series of tandem CAG repeats, Here we explore the ca pacity of complementary peptide nucleic acids (PNAs) to invade the CAG triplets of the AR and TBP genes in human prostatic cancer cells and show that the PNAs readily entered the nuclei of lysolecithin-permeabi lized cells and effectively inhibited sense transcription of unique AR and TBP DNA sequences downstream of the site of PNA;DNA hybridization , but not upstream of that site, These PNAs had Little or no effect on transcription of the c-myc gene, which lacks a CAG triplet domain. Co nversely, a PNA complementary to a unique sequence of the c-myc gene d id not inhibit transcription of the AR or TBP genes but did inhibit c- myc transcription. Comparisons of PNA effects on sense and antisense t ranscription of the AR, TBP, and c-myc genes confirm that progression of the RNA polymerase complex beyond the site of PNA DNA hybridization is impaired in both directions. Suppression of the AR gene results in refolding of a transcriptionally active nucleosome containing a uniqu e 17-mer AR DNA sequence.