Association of human papillomavirus type 16 E2 with Rad50-interacting protein 1 enhances viral DNA replication

Rad50-interacting protein 1 (Rint1) associates with the DNA damage response protein Rad50 during the S phase to G2/M transition and functions in radiation-induced G2 checkpoint control. It has also been demonstrated that Rint1 is essential in vesicle trafficking from the Golgi to the endoplasmic reticulum (ER) through interaction with Zeste-White 10 (ZW10). We have isolated a novel interaction between Rint1 and the human papillomavirus type 16 (HPV16) transcription and replication factor E2. E2 binds to Rint1 within its ZW10 interaction domain and we show that in the absence of E2, Rint1 is localized to the ER and associates with ZW10. E2 expression results in a disruption of Rint1-ZW10 interaction and an accumulation of nuclear Rint1 protein, coincident with a significant reduction in vesicle movement from the ER to Golgi. Interestingly, nuclear Rint1 protein and members of the Mre11/Rad50/Nbs1 (MRN) were found in distinct E2 nuclear foci, which peaked during mid-S phase, indicating that recruitment of Rint1 to E2 foci within the nucleus may also result in recruitment of this DNA damage sensing protein complex. We show that exogenous Rint1 expression enhances E2-dependent virus replication. Conversely, over-expression of a truncated Rint1 protein that retains the E2-binding domain but not the Rad50 binding domain acts as a dominant negative inhibitor of E2-dependent HPV replication. Put together, these experiments demonstrate that the interaction between Rint1 and E2 has an important function in HPV replication.