The UL138 protein localizes to the Golgi Apparatus.  Viruses lacking UL138 fail to maintain latency (they generate infectious particles in CD34+ cells where wild type clinical strain viruses are able to effectively suppress progeny virion formation).  The ability of UL138 to inhibit IE1 transcription in undifferentiated myeloid cells is likely responsible for its ability to help maintain latency.  UL138 silences IE gene expression during latency by preventing cellular lysine demtheylases (KDMs) and the CtBP1 protein from associating with the viral genome where they would remove repressive epigenetic marks.  UL138 also promotes the cell surface expression of the TNFR receptor and downregulates cell surface expression of the multidrug transporter MRP1.