Modification of papillomavirus E2 proteins by the small ubiquitin-like modifier family members (SUMOs)

The P protein of parainfluenza virus 5 (PIV5) is an essential cofactor of the viral RNA-dependent RNA polymerase. Phosphorylation of the P protein can positively or negatively regulate viral gene expression, depending on the precise phosphorylation sites. Sumoylation, a process of adding small ubiquitin-like modifier (SUMO) to proteins posttranslationally, plays an important role in regulating protein function. In this study, we have found that the P protein of PIV5 was sumoylated with SUMO1 in both transfected and infected cells. The K254 residue of the P protein is within a consensus sumoylation motif. Mutation of the P protein at K254 to arginine (P-K254R) reduced PIV5 minigenome activity, as well as the sumoylation level of the P protein. Incorporation of K254R into a recombinant PIV5 (rPIV5-P-K254R) resulted in a virus that grew to a lower titer and had lower levels of viral RNA synthesis and protein expression than wild-type PIV5, suggesting that sumoylation of the P protein at K254 is important for PIV5 growth. Biochemical studies did not reveal any defect of P-K254R in its interactions with viral proteins NP and L or formation of homotetramers. We propose that sumoylation of the P protein at K254 regulates PIV5 gene expression through a host protein.

Section: Discussionmentioning

confidence: 99%

Sumoylation of the P Protein at K254 Plays an Important Role in Growth of Parainfluenza Virus 5

Sun

2011

“…Apparently, exogenous overexpression of SUMO-2/3 with Ubc9 significantly stabilizes vE2 protein levels, whereas SUMO-1 fails to do so. This increase in stability is specific for vE2 but does not depend on covalent attachment of SUMO-2/3 to the viral protein, since inactivation of the predominantly modified lysine residue does not abolish the observed effect (193)(194)(195). This mechanism argues against simple competition between ubiquitin and SUMO for covalent attachment sites, rather suggesting that it is mediated through SUMOylation of a secondary cellular target(s).…”

Section: Herpesviridaementioning

confidence: 92%

Human Pathogens and the Host Cell SUMOylation System

Wimmer

Schreiner

Dobner

2012

108

101

Since posttranslational modification (PTM) by the small ubiquitin-related modifiers (SUMOs) was discovered over a decade ago, a huge number of cellular proteins have been found to be reversibly modified, resulting in alteration of differential cellular pathways. Although the molecular consequences of SUMO attachment are difficult to predict, the underlying principle of SUMOylation is altering inter-and/or intramolecular interactions of the modified substrate, changing localization, stability, and/or activity. Unsurprisingly, many different pathogens have evolved to exploit the cellular SUMO modification system due to its functional flexibility and far-reaching functional downstream consequences. Although the extensive knowledge gained so far is impressive, a definitive conclusion about the role of SUMO modification during virus infection in general remains elusive and is still restricted to a few, yet promising concepts. Based on the available data, this review aims, first, to provide a detailed overview of the current state of knowledge and, second, to evaluate the currently known common principles/molecular mechanisms of how human pathogenic microbes, especially viruses and their regulatory proteins, exploit the host cell SUMO modification system. Small ubiquitin-related modifier (SUMO) was initially identified as reversible, proteinogenic posttranslational modification (PTM) by different laboratories in the mid-1990s (13,116,122,125,135). Today, it is classified as a member of the ubiquitin-like proteins (Ubls) due to its structural and sequence similarities to ubiquitin (89, 169); however, the surface properties of SUMO are quite distinct. Interestingly, it appears that the characteristic determinants of PTM by Ubls are phylogenetically ancient and may have evolved from biosynthetic pathways via repeated rounds of gene duplication and diversification (75). Consequently, SUMO is expressed by all eukaryotes but is absent from prokaryotes/archaea. Lower eukaryotes have a single SUMO gene, whereas plants and vertebrates express several SUMO paralogues.In vertebrates, two subfamilies, namely, SUMO-1 and SUMO-2/3 proteins, are known. SUMO-2 and SUMO-3 are commonly referred to as SUMO-2/3 due to 98% sequence similarity and the lack, to date, of clearly distinguishable functional differences. Although members of each subfamily are highly similar, SUMO-1 and SUMO-2/3 share only about 50% amino acid sequence identity, although all are ϳ100-residue proteins containing significant primary sequence homology to ubiquitin in the C terminus (ϳ20%) and a short unstructured N-terminal stretch (11,128).Recent research has shown important differences in the molecular functionalities of mammalian SUMO-1 and SUMO-2/3 proteins. The latter is present in higher levels than SUMO-1, whereas the unconjugated pool of SUMO-1 is lower than that of SUMO-2/3. Intriguingly, SUMO-2 and SUMO-3 can be conjugated to target proteins in a chain-wise fashion due to internal SUMO conjugation motifs (SCMs), whereas SUMO-1 lacks this ability. Moreover...

“…BPV and HPV16 E2 are both bound by ubiquitin carrier protein 9 (Ubc9) (Y. C. Wu, Roark, Bian, & Wilson, 2008). The site of sumoylation is K292; which is conserved in the majority of alpha PVs, is important for E2 transcriptional regulation.…”

Section: E2 Post-translational Modificationsmentioning

confidence: 99%

Human Papillomavirus Replication Regulation by Acetylation of a Conserved Lysine in the E2 Protein

Thomas

Androphy

2018

iii ACKNOWLEDGEMENTS I would like to thank my supervisor Elliot J. Androphy for his guidance, and encouragement over these many years. I truly appreciate your faith and continuous support.I also want to thank all members of the Androphy lab, for your guidance, critiques, and support.Thank you to my thesis committee, without whom none of this would be possible.Your guidance has been invaluable. Michael Klemsz, Suk-Hee Lee, Lindsey Mayo, and Andy Yu. The Papillomavirus E2 protein is a sequence specific DNA binding protein that recruits cellular factors to its genome in infected epithelial cells. E2 also binds to and loads the viral E1 DNA helicase at the origin of replication. Post-translational modifications of PV E2 have been identified as potential regulators of E2 functions. We recently reported lysine (K) 111 as a target of p300 acetylation in B(bovine)PV that is involved in the regulation of viral transcription. K111 is conserved in most papillomaviruses, so we pursued a mutational approach to query the functional significance of lysine in HPV E2. Amino acid substitutions that prevent acetylation, including arginine, were unable to stimulate transcription and E1 mediated DNA replication. The arginine K111 mutant retained E2 transcriptional repression, nuclear localization, DNA and chromatin binding, and association with E2 binding partners involved in PV transcription and replication. v When directly investigating origin unwinding, the replication defective E2 K111R mutant recruited E1 to the viral replication origin, but surprisingly, unwinding of the duplex DNA did not occur. In contrast, the glutamine K111 mutant increased origin melting and stimulated replication compared to wild type E2. We have identified Topoisomerase I as a key host factor involved in viral replication whose recruitment is dependent on K111 acetylation, and propose a new model for viral origin dynamics during replication initiation. This work reveals a novel activity of E2 necessary for denaturing the viral origin that likely depends on acetylation of highly conserved lysine 111. Human Papillomaviruses and DiseaseThere are over 200 HPVs that have been described and they manifest in a variety of ways; they can be asymptomatic, or they can result in benign lesions (papillomas) or progress to malignancy (de Villiers, Fauquet, Broker, Bernard, & zur Hausen, 2004). In the United States, HPV is the most common sexually transmitted infection and nearly all sexually active adults contract it at least once. E1The PV E1 protein is an essential viral replication factor (Lusky & Botchan, 1985;Ustav, Ustav, Szymanski, & Stenlund, 1991). E1 is the viral helicase and initiates replication by binding to specific sequences on the viral genome with the assistance of the E2 protein (Frattini & Laimins, 1994).There is sequence and functional homology between PV E1 and SV (simian virus) 40 Large T Antigen which allowed for many of the predictions concerning E2 shows differential affinity for the E2BS and it is proposed that at low levels, E2b...