Generation of Left-handed Z-DNA in Solution and Visualization in Polytene Chromosomes by Immunofluorescence

Abstract

The prototype for left-handed, double-helical DNA in solution is provided by the synthetic polynucleotide poly[d(G-C)] exposed to high concentrations (>2.5 m) of NaCl (Pohl and Jovin 1972). However, numerous crystallographic and other studies documented in this volume and elsewhere have established the polymorphic nature of the Z family of left-handed conformations and delineated the numerous factors that can greatly enhance the probability of the B→Z transition: (1) increased ionic strength; (2) decreased water activity; (3) site-specific interactions of cations and anions; (4) increased temperature; (5) increased negative superhelical density; (6) binding of peptides and proteins, including poly amines, antibodies, and core histones (Miller et al., this volume); and (7) chemical modification of the DNA primary structure, such as substitution at the C-8 position of G, placement of a positive charge at N-7 of G, alkylation of the 2-amino group of G (Weaver and Tomasz 1982), methyl or bromine substitution at...