Interaction between the Drosophila CAF-1 and ASF1 chromatin assembly factors

The assembly of newly synthesized DNA into chromatin is essential for norma l growth, development, and differentiation. To gain a better understanding of the assembly of chromatin during DNA synthesis, we identified, cloned, a nd characterized the 180- and 105-kDa polypeptides of Drosophila chromatin assembly factor 1 (dCAF-1). The purified recombinant p180+p105+p55 dCAF-1 c omplex is active for DNA replication-coupled chromatin assembly. Furthermor e, 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 complex es 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 d CAF-1. Consistent with the interaction between dCAF-1 p105 and dASF1 in vit ro, we observed that dASF1 and dCAF-1 p105 colocalized in vivo in Drosophil a polytene chromosomes. This interaction between dCAF-1 and dASF1 may be a key component of the functional synergy observed between RCAF and dCAF-1 du ring the assembly of newly synthesized DNA into chromatin.