Fig. 1.
Positions of IRS1, IRS1263 and TRS1 open reading frames in the HCMV genome. The diagram at the top of the figure represents the entire HCMV genome. The terminal and internal repeat regions of the long unique (UL) segment of the genome (TRL and IRL, respectively) are represented as black boxes. The terminal and internal repeat regions of the short unique (US) segment of the genome (TRS and IRS, respectively) are represented as grey boxes. Dashed lines from the TRS and IRS regions of US lead to expanded areas showing the relative positions of the IRS1, IRS1263 and TRS1 coding sequences in the HCMV genome. Grey lines represent genome sequences in repeat regions; black lines represent genome sequences in the US segment. Arrows show the position and direction of transcription of the coding sequences. IRS1263 is the product of an alternative IRS1 transcript encoding the carboxyl terminus of IRS1 (aa 583–846) (Romanowski & Shenk, 1997).