Figure 2.

Suggested role of SUUR in replication and heterochromatin maintenance. In wild-type, SUUR protein moves through the chromatin together with the replisome (A). We suggest that SUUR controls the re-assembly of repressive chromatin on the daughter DNA strands thus preserving the chromatin state after the replication. This process is time-consuming and replication complex moves through the large heterochromatin blocks slowly. In polytene chromosomes this eventually results in under-replication. In SUUR mutants this control is turned off (B) and replisome progresses faster leading to complete polytenization of heterochromatin. However the repressive histone modifications are gradually diluted in SuUR mutants, as newly synthesized DNA strands incorporate histone marks randomly.