Some Observations on DNA Structure and Chromatin Organization at Specific Loci in Drosophila melanogaster
Within the eukaryotic nucleus, the DNA is packaged in a complex fashion by association with histones and other chromosomal proteins. One may suggest a priori that differential protein packaging of coding sequences at the broad level of the chromomere, or in the specific vicinity of a gene, or both, might be an important determinant in the selective expression of these sequences. Our goals have been to map features of chromatin structure relative to known functional sequences, to establish the presence of alternative patterns of structure during development, and to look for alterations in structure that might occur as part of the process of gene induction and repression. To this end, we have recently conducted a series of studies utilizing several different DNA-cleavage reagents to examine the patterns of DNA-protein interaction at a number of Drosophila genes. Concurrent studies using immunofluorescent staining of polytene chromosomes have identified several presumptive structural nonhistone chromosomal proteins, including some the distribution pattern of which indicates a preferential association with loci that are to be expressed at some point in the development of the salivary gland cells of Drosophila. We anticipate that the synthesis of this information may ultimately lead to a better understanding of the process of gene activation and hence provide insights into the regulation of this event during development. For a more thorough review of many of the issues raised herein, see Cartwright et al. (1982).
KeywordsChromatin Structure Polytene Chromosome Globin Gene Hypersensitive Site Micrococcal Nuclease
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