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A study to show that the Drosophila GAGA factor-FACT complex and its binding site, which downstream from the white gene are crucial fro, position effect variegation was conducted. The findings suggest that the GAGA factor and FACT-dependent replacement of Lys 9-methylated histone H3 by H3.3 counteracts the spreading of silent chromatin.

Deals with a study which showed that drosophila FACT (facilitates chromatin transcription) is associated with GAGA factor through its dSSRP1 subunit. Area where chromatin structure plays a critical role; Manner in which the identity of the body segment of metazoans is determined; Need for Hox gene expression patterns to be maintained.

Induction of aryl hydrocarbon hydroxylase by aryl hydrocarbons occurs only in neonatal rabbits and not in adult rabbits [Kahl, G. F., Friederich, D. E., Bigelow, S. W., Okey, A. B. & Nebert, D. W. (1980) Dev. Pharmacol.. Ther. l, 137-162]. In the present study, we isolated cDNA clones encoding aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (Arnt) from adult rabbits. The deduced amino acid sequences of rabbit AhR and Arnt showed 80% and 94% identities with those of human AhR and Arnt, respectively. Rabbit AhR mRNA was predominantly expressed in the lung and liver. in contrast, rabbit Arnt mRNA was expressed at almost the same level in all tissues except for the heart liver, and small intestine. Gel shift analysis showed that the AhR · Arnt complex could bind to the consensus xenobiotic-responsive element, which indicates that AhR expressed in adult rabbit livers possessed binding activity to the consensus xenobiotic-responsive element in vitro, although aryl hydrocarbons did not induce the activity of AHH in adult rabbits. We propose that the incapability of adult rabbits to induce cytochrome P-450 1A1 (CYP1A1) is caused by factors other than AhR and Arnt. [ABSTRACT FROM AUTHOR]

Members of the FOXO (forkhead O) class of transcription factors are tumor suppressors that also control aging and organismal life span. Mammalian FOXO degradation is proteasome-mediated, although the ubiquitin E3 ligase for FOXO factors remains to be defined. We show that MDM2 binds to FOXO1 and FOXO3A and promotes their ubiquitination and degradation, a process apparently dependent on FOXO phosphorylation at AKT sites and the E3 ligase activity of MDM2. Binding of MDM2 to FOXO occurs through the region of MDM2 that directs its cellular trafficking and the forkhead box of FOXO1. MDM2 promotes the ubiquitination of FOXO1 in a cell-free system, and its knockdown by small interfering RNA causes accumulation of endogenous FOXO3A protein in cells and enhances the expression of FOXO target genes. In cells stably expressing a temperature-sensitive p53 mutant, activation of p53 by shifting to permissive temperatures leads to MDM2 induction and degradation of endogenous FOXO3A. These data suggest that MDM2 acts as an ubiquitin E3 ligase, down-stream of p53, to regulate the degradation of mammalian FOXO factors. [ABSTRACT FROM AUTHOR]