Cytomegalovirus

Within the Herpesviridae, CMV belongs to the Betaherpesvirinae subfamily, which also includes the genera Muromegalovirus and Roseolovirus (human herpesvirus 6 and human herpesvirus 7). It is also related to other herpesviruses within the Alphaherpesvirinae subfamily, which includes herpes simplex viruses 1 and 2 and varicella-zoster virus, and the Gammaherpesvirinae subfamily, which includes Epstein–Barr virus and Kaposi's sarcoma-associated herpesvirus. SCCMV is called cercopithecine betaherpesvirus 5 (CeHV-5) and RhCMV, Cercopithecine betaherpesvirus 8 (CeHV-8). A further two viruses found in the night monkey are tentatively placed in the genus Cytomegalovirus, and are called Herpesvirus aotus 1 and Herpesvirus aotus 3. Rodents also have viruses previously called cytomegaloviruses that are now reclassified under the genus Muromegalovirus; this genus contains Mouse cytomegalovirus (MCMV) is also known as Murid betaherpesvirus 1 (MuHV-1) and the closely related Murid betaherpesvirus 2 (MuHV-2) that is found in rats. Species The following 11 species are assigned to the genus in ICTV 2022: • Cytomegalovirus aotinebeta1 • Cytomegalovirus cebinebeta1 • Cytomegalovirus cercopithecinebeta5 • Cytomegalovirus humanbeta5 • Cytomegalovirus macacinebeta3 • Cytomegalovirus macacinebeta8 • Cytomegalovirus mandrillinebeta1 • Cytomegalovirus paninebeta2 • Cytomegalovirus papiinebeta3 • Cytomegalovirus papiinebeta4 • Cytomegalovirus saimiriinebeta4 == Structure ==

Viruses in Cytomegalovirus are enveloped, with icosahedral, spherical to pleomorphic, and round geometries, and T=16 symmetry. The diameter is around 150–200 nm. Genomes are linear and nonsegmented, around 200 kb in length. == 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. == Life cycle ==

Viral replication is nuclear and lysogenic. Entry into the host cell is achieved by attachment of the viral glycoproteins to host receptors, which mediates endocytosis. Replication follows the dsDNA bidirectional replication model. DNA templated transcription, with some alternative splicing mechanism is the method of transcription. Translation takes place by leaky scanning. The virus exits the host cell by nuclear egress and budding. Humans and monkeys serve as the natural hosts. Transmission routes are dependent on coming into contact with bodily fluids (such as saliva, urine, and genital secretions) from an infected individual. All herpesviruses share a characteristic ability to remain latent within the body over long periods. Although they may be found throughout the body, CMV infections are frequently associated with the salivary glands in humans and other mammals. ==Genetic engineering==

The CMV promoter is commonly included in vectors used in genetic engineering work conducted in mammalian cells, as it is a strong promoter and drives constitutive expression of genes under its control. == History ==

Cytomegalovirus was first observed by German pathologist Hugo Ribbert in 1881 when he noticed enlarged cells with enlarged nuclei present in the cells of an infant. Years later, between 1956 and 1957, Thomas Huckle Weller together with Smith and Rowe independently isolated the virus, known thereafter as "cytomegalovirus". In 1990, the first draft of human cytomegalovirus genome was published, the biggest contiguous genome sequenced at that time. == See also ==