Amplified human MYC oncogenes localized to replicating submicroscopic circular DNA molecules.

Amplification of genes can sometimes be detected by molecular hybridization but not by cytogenetic methods, suggesting that in some cases the units of amplification may be too small to be detected by light microscopy. The experiments reported here investigate whether submicroscopic amplification units are present in early passages of the human tumor cell lines HL-60 and COLO 320. The results show that such cells do contain submicroscopic, extrachromosomal, supercoiled circular molecules harboring MYC genes.

Double minute chromosomes can be produced from precursors derived from a chromosomal deletion.

Recent experiments have shown that gene amplification can be mediated by submicroscopic, autonomously replicating, circular extrachromosomal molecules. We refer to those molecules as episomes (S. Carroll, P.

Recognition and repair of the CC-1065-(N3-adenine)-DNA adduct by the UVRABC nucleases.

The recognition and repair of the helix-stabilizing and relatively nondistortive CC-1065-(N3-adenine)-DNA adduct by UVRABC nuclease has been investigated both in vivo with phi X174 RFI DNA by a transfection assay and in vitro by a site-directed adduct in a 117 base pair fragment from M13mp1. CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis which binds within the minor groove of DNA through N3 of adenine. In contrast to the helix-destabilizing and distortive modifications of DNA caused by ultraviolet light or N-acetoxy-2-(acetylamino)fluorene, CC-1065 increases the melting point of DNA and decreases the S1 nuclease activity.

Demonstration of the asymmetric effect of CC-1065 on local DNA structure using a site-directed adduct in a 117-base-pair fragment from M13mp1.

Using DNase I and Alu I endonuclease analysis of a site-directed CC-1065-[N3-adenine]DNA adduct in a 117-base-pair fragment from M13mp1 DNA, we have demonstrated that CC-1065 produces an asymmetric effect on DNA conformation that extends more than one helix turn to the 5' side of the covalently modified adenine. CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis, which is believed to mediate its cytotoxic effects through covalent binding to DNA. Previous studies have demonstrated that CC-1065 binds covalently to N3 of adenine and lies within the minor groove of DNA spanning a 4-base-pair sequence to the 5' side of the modified adenine.

Construction and characterization of a site-directed CC-1065-N3-adenine adduct within a 117 base pair DNA restriction fragment.

The design, construction, and characterization of a site-directed CC-1065-N3-adenine adduct in a 117 base pair segment of M13mpI DNA are described. CC-1065 is an extremely potent antitumor antibiotic produced by Streptomyces zelensis. Previous studies have demonstrated that the cyclopropyl ring of CC-1065 reacts quite specifically with N3 of adenine in double-stranded DNA to form a CC-1065-DNA adduct.