Immunochemical analysis of the structure and function of chromosomal proteins

Abstract

Immunochemical approaches are useful in studying the nuclear organization and cellular function of chromosomal components. Antibodies specific to histones and to defined nonhistone proteins have been used to study nucleosome heterogeneity, to visualize the The structure of chromatin and chromosomes and the regulation of the genetic information encoded in DNA is largely dependent on a variety of interactions between the nucleic acid and protein components of the genome. In both interphase chromatin and metaphase chromosomes, the nucleoprotein fiber is built from a n array of repeating subunits, known as core particles, which contain about 146 base pairs of DNA complexed with two molecules of each histone H2A, H2B, H3, and H4. Adjacent core particles are covalently linked through a DNA segment, resulting in a fiberlike structure resembling a beaded string. The beaded chromatin fiber is further packed to yield the observed structure of chromatin and chromosomes (for reviews on chromatin structure see 15,18,26).Histones are the predominant class of nuclear proteins. Another class of nuclear proteins, collectively known as the nonhistone chromosomal proteins, is composed of a great number of molecular species. Members of this class of proteins are involved in various regulatory and structural aspects of the chromatin fiber. The chromatin fiber is a dynamic structure: gross morphological changes in the superstructure of the fiber, which occur during the cell cycle, are easily observable by light microscopy. The chromatin fiber is the substrate for the complex processes of transcription, replication, and repair. These metabolic processes often are accompanied by changes in the nonhistone protein constituents of the fiber and involve structural reorganization within the nucleosome. Furthermore, both the protein and the nucleic acid components of the chromatin fiber are subject to degradation, modification, and repair-processes which may alter the manner in which they interact with each other. Obviously, structural studies of the chromatin fiber have to take into account the dynamic properties of the complex and require techniques which can presence of histone in transcriptionally active chromatin, and to isolate DNA sequences associated with specific chromosomal proteins.Key terms: Histone, nonhistone, chromatin, an tibodies provide information on the native, in situ, organization of defined chromosomal components at various stages of chromatin organization.Because serological reactions occur under conditions which do not alter markedly the structure of chromatin and chromosomes, and since antibodies can react specifically with a n antigen under a variety of conditions, immunochemical approaches are uniquely suited for a variety of studies on the organization of nuclear proteins in the nucleoprotein fiber. Quantitative immunocytological techniques can be used to obtain information on local variations in antigen concentrations in metaphase and polytene chromsomes and in individual cell nuclei (1). Research involving immu...

Antibodies specific to histone H1 inhibitin vitro transcription in isolated mammalian nuclei

“…Such an approach has often been used in chromatin immunochemistry (for review see [26]). The fact that anti-H1 Fab fragments inhibited transcription almost completely confirms once again the main conclusion of our study.…”