Abstract
DNA supercoiling factor (SCF) is a protein capable of generating negative supercoils in DNA in conjunction with topoisomerase II. To clarify the biological functions of SCF, we introduced a heritable SCF RNAi into Drosophila. Upon knockdown of SCF, we observed male lethality and male-specific reduction in the expression levels of X-linked genes. SCF functionally interacts with components of the MSL complex, which are required for dosage compensation via hypertranscription of the male X chromosome. Moreover, SCF colocalizes with the MSL complex along the male X chromosome. Upon overexpression of SCF, the male X chromosome had a bloated appearance. This phenotype was dependent on the histone acetyltransferase MOF and was suppressed by simultaneous overexpression of ISWI. These findings demonstrate that SCF plays a role in transcriptional activation via alteration of chromatin structure and provide evidence that SCF contributes to dosage compensation.
Highlights
Both female X chromosomes are expressed in Drosophila
Knockdown of supercoiling factor (SCF) severely affects male viability To analyze the biological function of SCF, we attempted to perform RNA interference (RNAi) in vivo
We generated transgenic fly lines carrying a UAS-IRscf insert consisting of the GAL4-upstream activating sequence (UAS) and an inverted repeat (IR) of a part of the scf gene
Summary
Both female X chromosomes are expressed in Drosophila. To achieve dosage compensation, the single male X chromosome is hypertranscribed approximately twofold relative to the female X chromosomes. The products of these genes form an MSL complex that binds to numerous sites along the X chromosome, but in females the complex fails to assemble as a result of a translational block of the MSL-2 transcript by a protein called Sex-lethal (Bashaw and Baker, 1995; Kelley et al, 1995). In addition to these components, two noncoding RNAs, rox and rox, have been identified as members of the dosage compensation complex (Amrein and Axel, 1997; Meller et al, 1997; Franke and Baker, 1999). An essential histone H3 kinase, JIL-1, associates with the MSL complex (Jin et al, 2000; Wang et al, 2001)
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