NMR studies on the interaction of Replication Protein A 32 (RPA32) and TIPIN

Abstract

The RPA32 protein is involved in various DNA repair systems such as nucleotide excision repair (NER), base excision repair (BER), and homologous recombination. In these processes, RPA32 interacts with different binding partners at its C terminal common binding site (172-270; RPA32C). It has been reported recently that RPA32C also interacts with TIPIN during the intra-S checkpoint. During S phase TIM-TIPIN complex is present in replication foci and RPA32 facilitate the complex near the replication fork during the intra-S checkpoint. RPA32 facilitates the TIM-TIPIN complex, by direct interacting with TIPIN and the checkpoint response alleviates efficiently during the checkpoint response. Here, we show that TIPIN(185-218), which shares high sequence similarity with XPA(10-43) and UNG2(56-89), is disordered in free state and becomes structured upon binding to RPA32C with accompanying helix formation. The binding interface between TIPIN(185-218) and RPA32C is not exactly similar rather it has two binding sites compared to those of XPA- and UNG2-RPA32C complexes. Also, the binding affinities of those proteins towards RPA32C are comparable suggesting that DNA repair, homologous recombination, and checkpoint processes regulated by RPA32 in a competitive manner with comparable binding affinity.