Drosophila SUUR protein associates with PCNA and binds chromatin in a cell cycle-dependent manner

Drosophila SUUR (Suppressor of UnderReplication) protein was shown to regulate the DNA replication elongation process in endocycling cells. This protein is also known to be the component of silent chromatin in polyploid and diploid cells. To mark the different cell cycle stages, we used immunostaining patterns of PCNA, the main structural component of replication fork. We demonstrate that SUUR chromatin binding is dynamic throughout the endocyle in Drosophila salivary glands. We observed that SUUR chromosomal localization changed along with PCNA pattern and these proteins largely co-localized during the late S-phase in salivary glands. The hypothesized interaction between SUUR and PCNA was confirmed by co-immunoprecipitation from embryonic nuclear extracts. Our findings support the idea that the effect of SUUR on replication elongation depends on the cell cycle stage and can be mediated through its physical interaction with replication fork.