DrosophilaCAF-1 regulates HP1-mediated epigenetic silencing and pericentric heterochromatin stability

Abstract

SummaryChromatin assembly factor 1 (CAF-1) was initially characterized as a histone deliverer in the process of DNA-replication-coupled chromatin assembly in eukaryotic cells. Here, we report that CAF-1 p180, the largest subunit of Drosophila CAF-1, participates in the process of heterochromatin formation and functions to maintain pericentric heterochromatin stability. We provide evidence that Drosophila CAF-1 p180 plays a role in both classes of position effect variegation (PEV) and in the expression of heterochromatic genes. A decrease in the expression of Drosophila CAF-1 p180 leads to a decrease in both H3K9 methylation at pericentric heterochromatin regions and the recruitment of heterochromatin protein 1 (HP1) to the chromocenter of the polytene chromosomes. The artificial targeting of HP1 to a euchromatin location leads to the enrichment of Drosophila CAF-1 p180 at this ectopic heterochromatin, suggesting the mutual recruitment of HP1 and CAF-1 p180. We also show that the spreading of heterochromatin is compromised in flies that have reduced CAF-1 p180. Furthermore, reduced CAF-1 p180 causes a defect in the dynamics of heterochromatic markers in early Drosophila embryos. Together, these findings suggest that Drosophila CAF-1 p180 is an essential factor in the epigenetic control of heterochromatin formation and/or maintenance.

CAF-1 promotes Notch signaling through epigenetic control of target gene expression during Drosophila development

“…However, in eukaryotic cells the full transcription of a particular target gene is also dependent on the recruitment of chromatin remodelers and histone modifiers, in addition to transcription factors, in order to ensure a local chromatin environment that is permissive for the access of a complete set of regulatory proteins. Although CAF-1 was initially identified as a histone chaperone for DNA synthesis-coupled chromatin assembly (Smith and Stillman, 1989;Das et al, 2009), it is becoming increasingly evident that CAF-1 has functions in the regulation of other cellular and developmental processes, such as heterochromatin formation and asymmetric cell division (Quivy et al, 2008;Huang et al, 2010;Nakano et al, 2011). Recent studies in C. elegans and Arabidopsis imply that CAF-1 is involved in gene activation (Autran et al, 2011;Nakano et al, 2011); however, the precise mechanisms by which CAF-1 mediates gene activation and whether CAF-1 specifically regulates gene expression in association with a particular developmental pathway remain unclear.…”

“…Anti-acetylated H4 (Upstate Biotechnology), anti-dCAF-1-p105 (Antiomics), anti-H3 (Abcam) or anti-Su(H) (Santa Cruz) together with protein A/G agarose beads were incubated with sonicated lysates at 4°C overnight. Following elution (Huang et al, 2010), cross-linking of the chromatin samples was reversed at 65°C for 6 hours. Subsequently, genomic DNA was extracted and used as PCR template for quantitative analyses.…”

“…Increasing evidence suggests that CAF-1 has important functions in other cellular and developmental processes in addition to DNA replication (Ridgway and Almouzni, 2000;Groth et al, 2007;Quivy et al, 2008;Huang et al, 2010;Autran et al, 2011;Nakano et al, 2011). For example, it is involved in the restoration of chromatin structure after DNA repair (Groth et al, 2007;Chen et al, 2008;Li et al, 2008); CAF-1 also participates in the establishment of epigenetic information during heterochromatin formation (Song et al, 2007;Quivy et al, 2008;Huang et al, 2010); recent studies in Arabidopsis and C. elegans suggest that CAF-1 is involved in the regulation of gene expression as well as asymmetric cell division (Autran et al, 2011;Nakano et al, 2011). However, the molecular mechanisms by which CAF-1 regulates transcription and whether this function is coupled to specific signaling pathways that are essential for animal development remain unclear.…”

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

“…Su(var)3-3/dLSD1 Reuter et al 1986;Rudolph et al 2007 10 (8) et al 1993;Weiler 2007;Guruharsha et al 2011 Murzina et al 1999;Quivy et al 2004;Huang et al 2010 20 ( The top interacting proteins detected across the HP1a-BioTAP pull-downs in S2 cells and different life stages of the fly are listed, with S2 total peptide counts shown as representative data (unique counts in parentheses). Please see http://pklab.med.harvard.edu/ mass.spec/viewms.html for the counts in other life stages.…”

Screen for reactivation of MeCP2 on the inactive X chromosome identifies the BMP/TGF-β superfamily as a regulator of XIST expression

“…Mutations in DNA replication factors lead to defects in position-effect variegation in flies (36)(37)(38) and silencing defects at telomeres and silent mating loci in yeast (39)(40)(41). Likewise, perturbations of cellular acyl pools in yeast by genetic inactivation orthologs of Acaca (42) and Acss1 (43) cause global alterations in histone acetylation and genomewide expression.…”