Abstract
The subdivision of polytene chromosomes into bands and interbands suggests a structural chromatin organization that is related to the formation of functional domains of gene expression. We made use of the antibody Z4 to gain insight into this level of chromosomal structure, as the Z4 antibody mirrors this patterning by binding to an antigen that is present in most interbands. The Z4 gene encodes a protein with seven zinc fingers, it is essential for fly development and acts in a dose-dependent manner on the development of several tissues. Z4 mutants have a dose-sensitive effect on w(m4) position effect variegation with a haplo-suppressor and triplo-enhancer phenotype, suggesting Z4 to be involved in chromatin compaction. This assumption is further supported by the phenotype of Z4 mutant chromosomes, which show a loss of the band/interband pattern and are subject to an overall decompaction of chromosomal material. By co-immunoprecipitations we identified a novel chromo domain protein, which we named Chriz (Chromo domain protein interacting with Z4) as an interaction partner of Z4. Chriz localizes to interbands in a pattern that is identical to the Z4 pattern. These findings together with the result that Z4 binds directly to DNA in vitro strongly suggest that Z4 in conjunction with Chriz is intimately involved in the higher-order structuring of chromosomes.
Highlights
For several structural and functional reasons the enormous size of eukaryotic genomes has to be folded into chromatin in a hierarchical fashion
The subdivision of polytene chromosomes into bands and interbands suggests a structural chromatin organization that is related to the formation of functional domains of gene expression
We made use of the antibody Z4 to gain insight into this level of chromosomal structure, as the Z4 antibody mirrors this patterning by binding to an antigen that is present in most interbands
Summary
For several structural and functional reasons the enormous size of eukaryotic genomes has to be folded into chromatin in a hierarchical fashion. It basically states that stretches of chromatin form topologically discrete units, chromatin loops which may be further compacted according to their state in gene expression. It is proposed in this model that the bases of the loops are formed by the local interaction of sequences which are far apart in the linear DNA. Such sequences, called boundary sequences, may have certain physiological functions, like that of insulator or blocking elements to shield the regulatory influence of flanking domains. Boundary elements were proposed to have a role for the attachment of looped domains to an as yet ill-defined nuclear skeleton
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
