SUMO-1 Modification of Bovine Papillomavirus E1 Protein Is Required for Intranuclear Accumulation

Dhandapani Rangasamy,Kelly Woytek,Saleem A Khan,Van G Wilson

doi:10.1074/jbc.m007777200

Dhandapani Rangasamy, Kelly Woytek + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m007777200

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Abstract

The E1 protein is a multifunctional, origin-binding helicase that is essential for replication of papillomaviruses. Recently, bovine papillomavirus E1 was shown to be post-translationally modified by the addition of the SUMO-1 polypeptide. Here we show that the site of sumoylation maps to lysine residue 514. This lysine and the flanking sequences are well conserved in human papillomavirus (HPV) E1 proteins. Both HPV1a and HPV18 E1 proteins are substrates for sumoylation in vitro, which is consistent with this modification being a general property of E1 proteins. Mutations, which impair the sumoylation of bovine papillomavirus E1, prevent normal nuclear accumulation of E1 with a concomitant loss of replication capacity. These results suggest that sumoylation plays a role in nuclear transport and could regulate the E1 replication function by controlling access to the nuclear replication domains.

Highlights

Bovine papillomavirus (BPV)1 E1 protein is the major initiator protein for viral DNA replication and plays a critical role in the establishment of episomal viral genomes in the host cell nucleus [1]
Requirements for SUMO-1 Conjugation of E1—The BPV E1 protein interacts with the Ubc9-conjugating enzyme and is modified by the addition of SUMO-1 both in vitro and in vivo
The apparent interaction in the two-hybrid system probably represents a low level of covalent attachment of SUMO-1 to E1 protein via the endogenous yeast homolog of hUbc9 [31] rather than a noncovalent association

Summary

Introduction

Bovine papillomavirus (BPV)1 E1 protein is the major initiator protein for viral DNA replication and plays a critical role in the establishment of episomal viral genomes in the host cell nucleus [1]. To further understand the role of E1 sumoylation, this study identified the major SUMO-1 attachment site in the BPV E1 protein and evaluated the functional properties of mutants defective in sumoylation. E1 mutants defective in Ubc9 interaction or lacking the SUMO-1 attachment lysine all demonstrated impaired replication as a consequence of defective nuclear localization.

Results

Conclusion