Interaction between the DrosophilaCAF-1 and ASF1 Chromatin Assembly Factors

Abstract

The assembly of newly synthesized DNA into chromatin is essential for normal growth, development, and differentiation. To gain a better understanding of the assembly of chromatin during DNA synthesis, we identified, cloned, and characterized the 180-and 105-kDa polypeptides of Drosophila chromatin assembly factor 1 (dCAF-1). The purified recombinant p180؉p105؉p55 dCAF-1 complex is active for DNA replicationcoupled chromatin assembly. Furthermore, we have established that the putative 75-kDa polypeptide of dCAF-1 is a C-terminally truncated form of p105 that does not coexist in dCAF-1 complexes containing the p105 subunit. The analysis of native and recombinant dCAF-1 revealed an interaction between dCAF-1 and the Drosophila anti-silencing function 1 (dASF1) component of replication-coupling assembly factor (RCAF). The binding of dASF1 to dCAF-1 is mediated through the p105 subunit of dCAF-1. Consistent with the interaction between dCAF-1 p105 and dASF1 in vitro, we observed that dASF1 and dCAF-1 p105 colocalized in vivo in Drosophila polytene chromosomes. This interaction between dCAF-1 and dASF1 may be a key component of the functional synergy observed between RCAF and dCAF-1 during the assembly of newly synthesized DNA into chromatin.

Chromatin assembly factor 1 ensures the stable maintenance of silent chromatin states in Arabidopsis

“…Indeed, the most prominent feature of fas mutants is the stochastic occurrence of the various pleiotropic phenotypes (Leyser & Furner 1992;Kaya et al 2001), which appear to be reinforced by additional mutations in either one of two anti-silencing function1 (ASF1) orthologues in Arabidopsis, AtASF1a and AtASF1b (our unpublished observation). ASF1 is a histone H3-H4 binding protein known to facilitate CAF-1-dependent nucleosome assembly probably via its interaction with the second largest subunit of CAF-1 (Tyler et al 1999(Tyler et al , 2001. In higher eukaryotes, many developmental genes in euchromatic regions are also repressed by compaction into a heterochromatin-like structure and are kept silent throughout the course of development unless required.…”

Chromatin disassembly and reassembly during DNA repair

“…1A). The functional coordination between Asf1 and CAF-1 during chromatin assembly may be mediated via the direct physical interaction between these proteins [15][16][17] (Fig. 1A).…”

Histone deposition protein Asf1 maintains DNA replisome integrity and interacts with replication factor C

“…The best characterized replication-coupled chromatin assembly factor is chromatin assembly factor-1 (CAF-1), an evolutionarily conserved protein complex that binds histone H3 and H4 and delivers them to replicating DNA through an interaction with proliferating cell nuclear antigen (PCNA), the DNA polymerase processivity protein (for review, see Asf1, another evolutionarily conserved histone chaperone, functions during both replication-coupled and replication-independent chromatin assembly. Asf1 bound to histones H3/H4 stimulates histone deposition by CAF-1 in vitro (Tyler et al 1999;Sharp et al 2001), and Asf1 physically interacts with the p60/Cac2 subunit of CAF-1 (Tyler et al 2001;Krawitz et al 2002;Mello et al 2002). In yeast, Asf1 and the Hir proteins directly interact and function together to promote heterochromatic gene silencing (Kaufman et al 1998;Sharp et al 2001;Sutton et al 2001;Krawitz et al 2002).…”