To identify functional domains of HSV-1 gH, we generated 22 randomized linker-insertion mutants. Analyses of 22 gH mutants revealed that gH is relatively tolerant of insertion mutations, as 15 of 22 mutants permitted normal processing and transport of gH-gL to the cell surface. gH mutants that were not expressed well at the cell surface did not function in fusion or viral entry. The screening of gH mutants for function revealed the following: (i) for wild-type gH and some gH mutants,

fusion with nectin-1-expressing target cells occurred more rapidly than with herpesvirus entry mediator (HVEM)-expressing target cells; (ii) some gH mutants reduced the rate of cell fusion without abrogating fusion completely, indicating that gH may play a role in governing the kinetics of fusion and may be responsible for a rate-limiting first stage in HSV-1 check details fusion; and (iii) only one gH mutant, located within the short SC75741 cytoplasmic tail, completely abrogated function, indicating that the gH cytoplasmic tail is crucial for cell fusion and viral infectivity.”
“Replication and transcription activator (RTA) encoded by open reading frame 50 (ORF50) of Kaposi’s sarcoma-associated herpesvirus (KSHV) is essential and sufficient

to initiate lytic reactivation. RTA activates its target genes through direct binding with high affinity to its responsive elements or by interaction with cellular factors, such as RBP-J kappa, Ap-1, C/EBP-alpha, and Oct-1. In this study, we identified transducin-like enhancer of split 2 (TLE2) as a novel RTA binding protein by using yeast two-hybrid screening of a human spleen cDNA library. The interaction between TLE2 and RTA was confirmed by glutathione S-transferase (GST) binding and coimmunoprecipitation assays. Immunofluorescence analysis showed that TLE2 and RTA were colocalized in the same nuclear compartment in KSHV-infected cells. This interaction recruited TLE2 to RTA bound to its recognition sites on DNA and repressed

RTA auto-activation Nec-1s and transactivation activity. Moreover, TLE2 also inhibited the induction of lytic replication and virion production driven by RTA. We further showed that the Q (Gln-rich), SP (Ser-Pro-rich), and WDR (Trp-Asp repeat) domains of TLE2 and the Pro-rich domain of RTA were essential for this interaction. RBP-J kappa has been shown previously to bind to the same Pro-rich domain of RTA, and this binding can be subject to competition by TLE2. In addition, TLE2 can form a complex with RTA to access the cognate DNA sequence of the RTA-responsive element at different promoters. Intriguingly, the transcription level of TLE2 could be upregulated by RTA during the lytic reactivation process. In conclusion, we identified a new RTA binding protein, TLE2, and demonstrated that TLE2 inhibited replication and transactivation mediated by RTA.