tailieunhanh - Báo cáo khoa học: Histones in functional diversification Core histone variants

Recent research suggests that minor changes in the primary sequence of the conserved histones may become major determinants for the chromatin structure regulating gene expression and other DNA-related processes. An analysis of the involvement of different core histone variants in different nuclear processes and the structure of different variant nucleosome cores shows that this may indeed be so. Histone variants may also be involved in demarcating functional regions of the chromatin. | FEBS Journal REVIEW ARTICLE Histones in functional diversification Core histone variants Rama-Haritha Pusarla and Purnima Bhargava Centre for Cellular Molecular Biology Tarnaka Hyderabad India Keywords chromatin nucleosome histones gene expression histone variants Correspondence P. Bhargava Centre for Cellular Molecular Biology UppalRoad Tarnaka Hyderabad-500007 India Fax 91 40 27160591 Tel 91 40 27192603 E-mail purnima@ Received 6 July 2005 accepted 22 August 2005 Recent research suggests that minor changes in the primary sequence of the conserved histones may become major determinants for the chromatin structure regulating gene expression and other DNA-related processes. An analysis of the involvement of different core histone variants in different nuclear processes and the structure of different variant nucleosome cores shows that this may indeed be so. Histone variants may also be involved in demarcating functional regions of the chromatin. We discuss in this review why two of the four core histones show higher variation. A comparison of the status of variants in yeast with those from higher eukaryotes suggests that histone variants have evolved in synchrony with functional requirement of the cell. doi Introduction Eukaryotic cells package their DNA in the form of chromatin to accommodate it in the small space provided by their nuclei 1 . In spite of the 10 000-fold compaction of DNA due to this packaging minute details of a local structure regulate the accessibility of any small region. The folding of 147 bp of DNA over a histone octamer two molecules each of the four core histones H4 H3 H2A and H2B surface gives a neat organization of the DNA into a chromatin fibre of 10 nm diameter. The primary structure of 10 nm chromatin has a characteristic beads on a string appearance. This uniformity of the nucleosomal chain might impose difficulties in region-specific localized recognition and in uncoiling of the structure .