%0 Generic
%A Charapitsa, Iryna
%D 2009
%F heidok:9846
%K Chromatin , dosage compensation
%R 10.11588/heidok.00009846
%T Biochemical and Functional Characterisation of the Novel Non Specific Lethal Complex
%U https://archiv.ub.uni-heidelberg.de/volltextserver/9846/
%X Genomic DNA is not freely accessible but it is compacted into chromatin by wrapping DNA around a histone octamer. Basic unit of chromatin is a nucleosome. Accessibility of nucleosomal DNA highly regulated and is orchestrated by many proteins that combinatorially alter the positional phasing of nucleosomes by chromatin remodeling enzymes, substitution of variant histones, post-translational modification of nucleosomes and the partitioning of chromatin into specific nuclear locations.  X chromosomal regulation by the process of dosage compensation provides an ideal model system to study the effect of chromatin and epigenetic factors on gene expression. In mammals, genes on the active X (Xa) chromosome are upregulated about twofold, with a corresponding inactivation of one of the two X chromosomes (Xi) ensuring equivalent sex chromosome expression in males and females. In Drosophila, dosage compensation is accomplished by the work of the MSL complex, which provokes a two-fold increase in the expression of genes on the male X chromosome. The MSL complex specifically binds to genes that require to be unregulated and, through the action of MOF, a histone acetyltransferase subunit within the complex, induces acetylation of H4K16, which is associated with an increase in the rate of transcription of genes. In contradiction to the classic view that MOF was restricted to the male X chromosome, it has been found recently by our lab that MOF binds to multiple sites on the autosomes in both sexes. This suggests that MOF has a role in transcriptional regulation beyond dosage compensation. The work presented in this thesis shows the purification of a novel complex of evolutionary conserved proteins, which contains MOF. We termed the complex the NSL complex (Non-Specific Lethal), as mutation of proteins of the complex is lethal to both sexes. The NSL complex is composed of the evolutionary conserved proteins MOF, NSL1, NSL2, NSL3, MCRS2, MBDR2, WDS, Z4 and Chromator. These components of the NSL complex broadly decorate all chromosomes, and overlap with MOF on the X chromosome(s), as well as on all autosomes in males and females. Colocalization of NSL complex members with MOF occurs at the level of individual genes, with NSL associated with the promoters of MOF-bound genes. Analysis of total RNA from fly lines expressing RNAi against NSLs specifically in salivary glands demonstrates that the binding of the NSL complex to promoters is functional, as there is a strong correlation between the absence of NSL and a decrease in transcription in males and females. Taken together, work performed in this thesis demonstrates that the NSL complex functions as a novel transcription regulator in Drosophila.