LMP1-Induced Sumoylation Influences the Maintenance of Epstein-Barr Virus Latency through KAP1

ABSTRACT As a herpesvirus, Epstein-Barr virus (EBV) establishes a latent infection that can periodically undergo reactivation, resulting in lytic replication and the production of new infectious virus. Latent membrane protein-1 (LMP1), the principal viral oncoprotein, is a latency-associated protein implicated in regulating viral reactivation and the maintenance of latency. We recently found that LMP1 hijacks the SUMO-conjugating enzyme Ubc9 via its C-terminal activating region-3 (CTAR3) and induces the sumoylation of cellular proteins. Because protein sumoylation can promote transcriptional repression, we hypothesized that LMP1-induced protein sumoylation induces the repression of EBV lytic promoters and helps maintain the viral genome in its latent state. We now show that with inhibition of LMP1-induced protein sumoylation, the latent state becomes less stable or leakier in EBV-transformed lymphoblastoid cell lines. The cells are also more sensitive to viral reactivation induced by irradiation, which results in the increased production and release of infectious virus, as well as increased susceptibility to ganciclovir treatment. We have identified a target of LMP1-mediated sumoylation that contributes to the maintenance of latency in this context: KRAB-associated protein-1 (KAP1). LMP1 CTAR3-mediated sumoylation regulates the function of KAP1. KAP1 also binds to EBV OriLyt and immediate early promoters in a CTAR3-dependent manner, and inhibition of sumoylation processes abrogates the binding of KAP1 to these promoters. These data provide an additional line of evidence that supports our findings that CTAR3 is a distinct functioning regulatory region of LMP1 and confirm that LMP1-induced sumoylation may help stabilize the maintenance of EBV latency. IMPORTANCE Epstein-Barr virus (EBV) latent membrane protein-1 (LMP1) plays an important role in the maintenance of viral latency. Previously, we documented that LMP1 targets cellular proteins to be modified by a ubiquitin-like protein (SUMO). We have now identified a function for this LMP1-induced modification of cellular proteins in the maintenance of EBV latency. Because latently infected cells have to undergo viral reactivation in order to be vulnerable to antiviral drugs, these findings identify a new way to increase the rate of EBV reactivation, which increases cell susceptibility to antiviral therapies

The Epstein-Barr Virus (EBV) Deubiquitinating Enzyme BPLF1 Reduces EBV Ribonucleotide Reductase Activity▿

A newly discovered virally encoded deubiquitinating enzyme (DUB) is strictly conserved across the Herpesviridae. Epstein-Barr virus (EBV) BPLF1 encodes a tegument protein (3,149 amino acids) that exhibits deubiquitinating (DUB) activity that is lost upon mutation of the active-site cysteine. However, targets for the herpesviral DUBs have remained elusive. To investigate a predicted interaction between EBV BPLF1 and EBV ribonucleotide reductase (RR), a functional clone of the first 246 N-terminal amino acids of BPLF1 (BPLF1 1-246) was constructed. Immunoprecipitation verified an interaction between the small subunit of the viral RR2 and BPLF1 proteins. In addition, the large subunit (RR1) of the RR appeared to be ubiquitinated both in vivo and in vitro; however, ubiquitinated forms of the small subunit, RR2, were not detected. Ubiquitination of RR1 requires the expression of both subunits of the RR complex. Furthermore, coexpression of RR1 and RR2 with BPLF1 1-246 abolishes ubiquitination of RR1. EBV RR1, RR2, and BPLF1 1-246 colocalized to the cytoplasm in HEK 293T cells. Finally, expression of enzymatically active BPLF1 1-246 decreased RR activity, whereas a nonfunctional active-site mutant (BPLF1 C61S) had no effect. These results indicate that the EBV deubiquitinating enzyme interacts with, deubiquitinates, and influences the activity of the EBV RR. This is the first verified protein target of the EBV deubiquitinating enzyme

Examining different forms of implementation and in early childhood curriculum research

The purpose of this study was to examine different approaches to assessing implementation in an early childhood curriculum research study. Early childhood teachers in 51 preschool classes located at nationally dispersed sites implemented the Children's School Success curriculum for a school year. Structural (proportion of curriculum delivered) and process (quality of delivery of curriculum) measures of implementation were collected for the literacy, math, and social components of the curriculum. Also, a multiplicative composite score incorporating information from the structural and process measures was calculated. Site differences occurred for the process measure, but not the structural and composite measures. Analysis of the process implementation measures collected across time revealed primarily stable trends across sites. Significant associations were found between measures of implementation and some of the child outcome variables, with the different forms of implementatio