XNP/dATRX interacts with DREF in the chromatin to regulate gene expression

Abstract

The ATRX gene encodes a chromatin remodeling protein that has two important domains, a helicase/ATPase domain and a domain composed of two zinc fingers called the ADD domain. The ADD domain binds to histone tails and has been proposed to mediate their binding to chromatin. The putative ATRX homolog in Drosophila (XNP/dATRX) has a conserved helicase/ATPase domain but lacks the ADD domain. In this study, we propose that XNP/dATRX interacts with other proteins with chromatin-binding domains to recognize specific regions of chromatin to regulate gene expression. We report a novel functional interaction between XNP/dATRX and the cell proliferation factor DREF in the expression of pannier (pnr). DREF binds to DNA-replication elements (DRE) at the pnr promoter to modulate pnr expression. XNP/dATRX interacts with DREF, and the contact between the two factors occurs at the DRE sites, resulting in transcriptional repression of pnr. The occupancy of XNP/dATRX at the DRE, depends on DNA binding of DREF at this site. Interestingly, XNP/dATRX regulates some, but not all of the genes modulated by DREF, suggesting a promoter-specific role of XNP/dATRX in gene regulation. This work establishes that XNP/dATRX directly contacts the transcriptional activator DREF in the chromatin to regulate gene expression.

Single cell analysis of Daxx and ATRX-dependent transcriptional repression

“…Daxx has previously been reported to bind to and/or transcriptionally repress cellular and viral promoters, including c-met, RelB target genes and CMV (Croxton et al, 2006;Morozov et al, 2008;Puto and Reed, 2008;Reeves et al, 2010;Zhang et al, 2010). It is not known whether ATRX is required for the Daxx-mediated repression of these genes, however, the Drosophila ATRX homolog was recently shown to repress the pannier gene through a promotermediated mechanism (Valadez-Graham et al, 2012). Additionally, the mutually exclusive enrichment of active factors, including RNA pol II, and repressive factors, including Daxx, at the promoters of the murine CMV immediate early (IE) genes during the lytic and latent phases of infection, respectively (Liu et al, 2010), is reminiscent of our result showing that RNA pol II accumulation at the activated array is significantly reduced by ATRX expression in the U2OS cell line.…”

Heterochromatin-associated interactions of Drosophila HP1a with dADD1, HIPP1, and repetitive RNAs

“…This recognition was enhanced by interaction with HP1a, which also recognizes the same epitope, although likely on a neighboring nucleosome (Dhayalan et al 2011;Iwase et al 2011). Given that the fly homolog of ATRX, XNP, lacks an ADD domain (Bassett et al 2008;Valadez-Graham et al 2012), we wanted to explore the possible link between the CG8290 ADD, HP1a, and H3K9me2/3 recognition.…”

Physical and Functional Interactions between Drosophila Homologue of Swc6/p18Hamlet Subunit of the SWR1/SRCAP Chromatin-remodeling Complex with the DNA Repair/Transcription Factor TFIIH

“…Yeast mating was conducted, and colony selection was performed on minimal standard medium without His, Leu, and Trp (Clontech), supplemented with 2.5 mM 3-amino-1,2,4-triazole after 7 days. Finally, positive colonies were considered after ␣-and ␤-galactosidase enzymatic assays as reported previously (19,20).…”

“…GST Pull-down Assays and GST Pull-down Competition Assays-Pull-down assays were carried out as described previously (19). GST fusion proteins for full-length Dmp8 (GSTDmp8), Dmp52 (GST-Dmp52), and Dmp18 (GST-Dmp18) or its fragments (GST-Dmp52(1-400), GST-Dmp52(401-500), GST-Dmp18(1-76), and GST-Dmp18(49 -152)) were produced by cloning each sequence onto the pGEX4T-1 vector (Stratagene) and expressed in BL-21-competent bacterial cells.…”