Selective blockage of the 3'-->5' exonuclease activity of WRN protein by certain oxidative modifications and bulky lesions in DNA.

Individuals with mutations in the WRN gene suffer from Werner syndrome, a disease with early onset of many characteristics of normal aging. The WRN protein (WRNp) functions in DNA metabolism, as the purified polypeptide has both 3'-->5' helicase and 3'-->5' exonuclease activities. In this study, we have further characterized WRNp exonuclease activity by examining its ability to degrade double-stranded DNA substrates containing abnormal and damaged nucleo-tides.

The roles of specific template nucleosides in the formation of stable transcription complexes by Escherichia coli RNA polymerase.

We have examined the effects of removing individual template nucleosides on promoter escape by Escherichia coli RNA polymerase in vitro. The ability of DNA templates containing random single nucleoside gaps generated by hydroxyl radical treatment to support the production of stable ternary transcription complexes was analyzed. On two templates containing different promoter and initial transcribed regions, we found that removal of nucleosides on the template strand in the region from -13 to at least +8 relative to the transcription start site interfered with ternary complex formation.

Effect of the crystallizing agent 2-methyl-2,4-pentanediol on the structure of adenine tract DNA in solution.

The hydroxyl radical cleavage pattern of bent DNA containing phased adenine tracts has a sinusoidal pattern. Changes in the cleavage pattern of the sequence A5N5 in the presence of 2-methyl-2,4-pentanediol (MPD) demonstrate that MPD has an effect on the structure of a bent A-tract region of DNA. The effect of MPD on DNA structure appears to be limited to bent A-tract regions, as we find no significant changes in the cleavage pattern of flanking regions, mixed-sequence DNA, or the unbent A-tract sequence T4A4N2.