The Rep68 protein of adeno-associated virus type 2 increases RNA levels from the human cytomegalovirus major immediate early promoter

The Rep68 and Rep78 proteins of adeno-associated virus type-2 (AAV) are multifunctional DNA binding proteins which are involved in the positive and negative regulation of AAV genes, as well as various cellular and heterologous viral genes. In this study we report that Rep68 enhances expression from the major immediate early promoter (MIEP) or human cytomegalovirus (HCMV). This Rep-mediated enhancement of RNA levels is abrogated by the introduction of a Rep recognition sequence (RRS) at either position -18 or -244 in the HCMV-M[EP. However, a mutant RRS (mRRS), which is not bound by Rep68 is unable to negate the effect of Rep68. Sequence analysis and electrophoretic mobility shift assays showed no Rep68 binding sites within the wild-type HCMV-MIEP. Rep68 may therefore be enhancing expression from the HCMV-MIEP by interacting with other regulatory proteins that have an effect on the expression from this promoter or by altering the expression of a cellular gene whose product influences the HCMV-MIEP. Our results may also help to explain the previous observation that coinfection with AAV enhances the cytopathic effect of HCMV. (C) 1997 Academic Press.