By the use of psoralen crosslinking and primer extension, a method was developed which allows the analysis of chromatin structure in vivo. Using a yeast minichromosome, >9 nucleosomes were mapped with a resolution of at least +/-30 bp.

The binding of two psoralen derivatives to DNA and to chromatin has been compared in some detail, particularly with respect to the influence of the ionic environment. The compounds used were the extremely hydrophobic 4,5’,8-trimethylpsoralen (TMP) and its extremely hydrophilic derivative 4’-aminomethyl-4,5’,8-trimethylpsoralen (AMT). Both the dark noncovalent interaction and the UV light induce...

DNA intercalators are planar molecules that insert between the base pairs of duplex DNA. Intercalation into DNA necessarily results in changes in DNA conformation, separating base pairs along the helical axis; thus, intercalators are of great importance as probes of nucleic acid structure and as interferents of DNA replication, transcription, and/or topoisomerase activities. Relationships betwe...

UV irradiation has been shown to activate the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in cell culture; however, only limited studies have been described in vivo. UV light has been categorized as UV-A (400 to 315 nm), -B (315 to 280 nm), or -C (less than 280 nm); the longer wavelengths are less harmful but more penetrative. Highly penetrative UV-A radiation constit...

We searched for nucleotide excision repair in human cell-free extracts using two assays: damage-specific incision of DNA (the nicking assay) and damage-stimulated DNA synthesis (the repair synthesis assay). HeLa cell-free extract prepared by the method of Manley et al. (1980) has a weak nicking activity on UV irradiated DNA and the nicking is only slightly reduced when pyrimidine dimers are eli...

DNA interstrand cross-links are complex lesions that covalently link both strands of the duplex DNA. Lesion removal is proposed to be initiated via the UvrABC nucleotide excision repair complex; however, less is known about the subsequent steps of this complex repair pathway. In this study, we characterized the contribution of nucleotide excision repair mutants to survival in the presence of ps...

Cells of a V79 subline of the Chinese hamster were microirradiated at wavelength 365 nm in the presence of the psoralen derivative, trioxsalen. Microirradiation was accomplished by a pulsed argon laser microbeam either in anaphase or in interphase 3 hr after mitosis. Inhibition of clonal growth and formation of micronuclei at the first postirradiation mitosis were observed after microirradiatio...