Editing Cytomegalovirus (section)

== Genome ==
[[File:HCMV genome.png|thumb|Class E genome of HCMV. The unique long and unique short regions are indicated as UL and US. Repeat regions are indicated as a, b and c sequences, where primes designate inverted orientations. Sequences ''ab'' and ''b′a′'' correspond to the terminal/internal repeat long (TRL/IRL); sequences ''a′c′'' and ''ca'' correspond to the internal/terminal repeat short (IRS/TRS). '''Top''': typical genome arrangement of wild-type strains; '''bottom''': genome arrangement of strain AD169, a laboratory-adapted strain. Genome rearrangements that have occurred during extensive passaging are indicated in red between the wild-type and laboratory-adapted configurations.<ref name=":0" />|alt=|400px]]

Herpesviruses have some of the largest genomes among human viruses, often encoding hundreds of proteins. For instance, the double‑stranded DNA (dsDNA) [[genome]] of wild-type HCMV strains has a size of around 235 kb and encodes at least 208 proteins. It is thus longer than all other human herpesviruses and one of the longest genomes of all human viruses in general. It has the characteristic herpesvirus class E genome architecture, consisting of two unique regions (unique long UL and unique short US), both flanked by a pair of inverted repeats (terminal/internal repeat long TRL/IRL and internal/terminal repeat short IRS/TRS). Both sets of repeats share a region of a few hundred bps, the so-called "a sequence"; the other regions of the repeats are sometimes referred to as "b sequence" and "c sequence".<ref name=":0">{{cite journal | vauthors = Sijmons S, Van Ranst M, Maes P | title = Genomic and functional characteristics of human cytomegalovirus revealed by next-generation sequencing | journal = Viruses | volume = 6 | issue = 3 | pages = 1049–1072 | date = March 2014 | pmid = 24603756 | pmc = 3970138 | doi = 10.3390/v6031049 | doi-access = free }}</ref>