DNA bending and curvature: a 'turning point' in DNA function?

Abstract

The genomic DN in the cell is tightly packed and is involved invarious functions like trancription, replication and recombination. As a response to the functional requirements as well as differnent environments inthe cell, DNA is known to undergo a number of structural variations from a canonical, uniform, righthanded double-helical B-DNA structure (watson & crick 1953). One such structural characteristic of DNA, which is the focus of this review, is DNA curvature and bending. A curved DNA is defined as a double stranded DNA with a nearly smoothly curved helical axix. In the last twenty years, the significance of DNA curvature and bending is different biological functions has been elucidated. A number of experiments have shown presence of curved DNA in many promoter regions and the importance of DNA curveture in the process of transcription has become clearly evident. Many analyses suggest that the curved DNA segments in the promoter region act as transcriptional signals and thus play a role in regulation of gene expression. Various aspects of DNA curvature and bending, related to transcriptin, replication and necleosome formation have been reviewed previously, but there have been many new developments in this field in recent days. In addition, with the availability of a large amount of genomic data, an understanding of the structural characteristics of DNA and their functional role has become even more important. in the post-genomic era, when gene prediction has emerged as a very great challenge, identifying additional structurel signals will help in improving the success rate of existing algorithms and new efforts ar being made to include "curvature signals" in these programs. In this reveew, we aim to provide an overview of the recent developments in the ield of DNA curvature and bending, in both 'in vitro' as well as 'in vivo' research. The 'in silico' predictions and their importance in post-genome era are also discussed.