[Ability of Su(Hw) to create a platform for ORC binding does not depend on the type of surrounding chromatin].

DNA replication begins from multiple sites distributed thoughout the genome and named replication origins. Despite the increasing amount of data on the properties of replication origins, it is still unknown what factors(s) is the primary determinant of ORC localization. Su(Hw) is a zinc-finger protein that is responsible for the activity of the best-studied Drosophila insulators. Here, we show that insulator protein Su(Hw) recruits histone acetyltransferase complex SAGA and chromatin remodeler dSWI/SNF to Su(Hw)-dependent insulators and creates platform for ORC binding. We have found that Su(Hw) is necessary for chromatin remodeling and ORC recruitment regardless of type of surrounding chromatin. Thus, global chromatin state does not influence molecular mechanism underlying ORC positioning in the genome, rather DNA-binding proteins are key determinants that create proper chromatin structure for ORC binding. Su(Hw) is the first example of such a protein.