Increased association between Epstein-Barr virus EBNA2 from type 2 strains and the transcriptional repressor BS69 restricts EBNA2 activity

Abstract

Natural variation separates Epstein-Barr virus (EBV) into type 1 and type 2 strains. Type 2 EBV is less transforming in vitro due to sequence differences in the EBV transcription factor EBNA2. This correlates with reduced activation of the EBV oncogene LMP1 and some cell genes. Transcriptional activation by type 1 EBNA2 can be suppressed through the binding of two PXLXP motifs in its transactivation domain (TAD) to the dimeric coiled-coil MYND domain (CC-MYND) of the BS69 repressor protein (ZMYND11). We identified a third conserved PXLXP motif in type 2 EBNA2. We found that type 2 EBNA2 peptides containing this motif bound BS69 CC-MYND efficiently and that the type 2 EBNA2 TAD bound an additional BS69 CC-MYND molecule. Full-length type 2 EBNA2 also bound BS69 more efficiently in pull-down assays. Molecular weight analysis and low-resolution structures obtained using small-angle X-ray scattering showed that three BS69 CC-MYND dimers bound two molecules of type 2 EBNA2 TAD , in line with the dimeric state of full-length EBNA2 in vivo . Importantly, mutation of the third BS69 binding motif in type 2 EBNA2 improved B-cell growth maintenance and the transcriptional activation of the LMP1 and CXCR7 genes. Our data indicate that increased association with BS69 restricts the function of type 2 EBNA2 as a transcriptional activator and driver of B cell growth and may contribute to reduced B-cell transformation by type 2 EBV.

B cells infected with Type 2 Epstein-Barr virus (EBV) have increased NFATc1/NFATc2 activity and enhanced lytic gene expression in comparison to Type 1 EBV infection

“…Nevertheless, we cannot exclude the possibility that EBNA2 type-dependent regulation of NFATc1/NFATc2 expression is specific to LCLs and not present in the context of Burkitt lymphoma cells. Indeed, low levels of IRF4 in Burkitt lymphoma cells may render the ability of T1 EBNA2 to bind to ets-IRF4 combined elements (EICE sites) of little functional consequence [29,31]. Difference in the functions of the T1 versus T2 EBNA3 proteins are another likely mechanism by which the EBV type specific differences in lytic phenotype might occur.…”

“…The major previously reported phenotypic difference between T1 and T2 EBV infection in vitro is that T1 EBV transforms B cells more efficiently than T2 EBV; this difference was first reported to be due to a single amino acid difference (S442D) between the EBNA2 proteins that allows the T1 EBNA2 to bind to EICE sites and more efficiently activate several cellular genes and the LMP1 promoter [28][29][30][31][32]. A further mechanism involving an additional binding site in type 2 EBNA2 for the cell repressor BS69 has also been found [31]. In addition, T2 EBV was also recently reported to infect T cells more efficiently [33][34][35].…”

EBNA2 driven enhancer switching at the CIITA-DEXI locus suppresses HLA class II gene expression during EBV infection of B-lymphocytes

“…We were unable to show any direct physical association of EBNA2 with CIITA by CoIP, but it is possible that EBNA2 and CIITA compete for occupancy or that EBNA2 modulates CIITA function at the HLA-II regulatory elements. While EBNA2 is not thought to be a transcriptional repressor, it is known to interact with the co-repressor BS69 through the MYND domain [ 52 ]. Type 2 EBNA2 interacts more strongly with BS69 and this correlates with its reduced capacity to activate LMP1 and transform B-cells [ 52 ].…”

Genetic Patterns Found in the Nuclear Localization Signals (NLSs) Associated with EBV-1 and EBV-2 Provide New Insights into Their Contribution to Different Cell-Type Specificities

“…The two types have functional differences in their ability to transform human B cells. EBV-1 induces the continuous proliferation (known as “transformation”) of human B cells more efficiently than EBV-2 in vitro [ 8 , 9 ]. Although EBV-2 has been associated with lower efficiency in immortalizing B lymphocytes in vitro, it has been detected in BL tumors [ 10 ].…”