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

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 pulldown assays.Molecular weight analysis and low-resolution structures obtained using smallangle 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. Author summaryEpstein-Barr virus (EBV) drives the development of many human cancers worldwide including specific types of lymphoma and carcinoma.EBV infects B lymphocytes and immortalises them, thus contributing to lymphoma development.The virus promotes B lymphocyte growth and survival by altering the level at which hundreds of genes are expressed.The EBV protein EBNA2 is known to activate many growth-promoting genes.