The Acidic Domain of pUL37x1 and gpUL37 Plays a Key Role in Transactivation of HCMV DNA Replication Gene Promoter Constructions

The tupaia herpesvirus (THV) was isolated from spontaneously degenerating tissue cultures of malignant lymphoma, lung, and spleen cell cultures of tree shrews (Tupaia spp.). The determination of the complete nucleotide sequence of the THV strain 2 genome resulted in a 195,857-bp-long, linear DNA molecule with a G؉C content of 66.5%. The terminal regions of the THV genome and the loci of conserved viral genes were found to be G؉C richer. Furthermore, no large repetitive DNA sequences could be identified. This is in agreement with the previous classification of THV as the prototype species of herpesvirus genome group F. The search for potential coding regions resulted in the identification of 158 open reading frames (ORFs) regularly distributed on both DNA strands. Seventy-six out of the 158 ORFs code for proteins that are significantly homologous to known herpesvirus proteins. The highest homologies found were to primate and rodent cytomegaloviruses. Biological properties, protein homologies, the arrangement of conserved viral genes, and phylogenetic analysis revealed that THV is a member of the subfamily Betaherpesvirinae. The evolutionary lineages of THV and the cytomegaloviruses seem to have branched off from a common ancestor. In addition, it was found that the arrangements of conserved genes of THV and murine cytomegalovirus strain Smith, both of which are not able to form genomic isomers, are colinear with two different human cytomegalovirus (HCMV) strain AD169 genomic isomers that differ from each other in the orientation of the long unique region. The biological properties and the high degree of relatedness of THV to the mammalian cytomegaloviruses allow the consideration of THV as a model system for investigation of HCMV pathogenicity.The family Herpesviridae comprises more than 100 different virus species with a worldwide occurrence in all taxonomic groups of vertebrates. The supposed roots of this virus family are in very early evolutionary times, and a long period of development has resulted in the appearance of extremely well host-adapted virus species (47,61,62,63), often more than one in a single host, for example, the eight different human herpesviruses HSV-1 (herpes simplex virus type 1), HSV-2, varizella-zoster virus, HCMV (human cytomegalovirus), EBV (Epstein-Barr virus), HHV-6 (human herpesvirus 6), HHV-7, and HHV-8, that are adapted to different cellular and molecular niches in the same host species (88).

Section: Discussionmentioning

confidence: 99%

Analysis and Characterization of the Complete Genome of Tupaia (Tree Shrew) Herpesvirus

Bahr

Darai

2001

“…These three proteins share the amino-terminal sequence because of alternative splicing and polyadenylylation of transcripts initiating at the same promoter and have been shown to be localized in the mitochondria as well as in the plasma membrane (9,11,17). The UL37-encoded proteins have been shown to transactivate selectively genes under control of both cellular and HCMV promoters and, more recently, have also been found to have antiapoptotic activities (10,12,17). It appears that the hydrophobic leader sequence and the acidic domain, both located within the first 120 amino acids at the amino terminus of these proteins, are responsible for the antiapoptotic and transcription regulation activities, respectively (10,12,17).…”

Section: Discussionmentioning

confidence: 99%

“…The products coded by UL37 are immediate-early membrane proteins localized in mitochondria as well as in the plasma membrane (1,11,12). The UL37 proteins have been shown to selectively transactivate the expression of genes under control of both cellular and HCMV promoters (10,12). More recently, these proteins have also been implicated to have antiapoptotic activities (17).…”

mentioning

confidence: 99%

Murine Cytomegalovirus Containing a Mutation at Open Reading Frame M37 Is Severely Attenuated in Growth and Virulence In Vivo

Lee

Xiao

Haghjoo

et al. 2000

A pool of murine cytomegalovirus (MCMV) mutants was generated by using a Tn3-based transposon mutagenesis procedure. One of the mutants, RvM37, which contained the transposon sequence at open reading frame M37, was characterized both in tissue culture and in immunocompetent BALB/c and immunodeficient SCID mice. Our results provide the first direct evidence to suggest that M37 is not essential for viral replication in vitro in NIH 3T3 cells. Compared to the wild-type strain and a rescued virus that restored the M37 region, the viral mutant was severely attenuated in growth in both BALB/c and SCID mice after intraperitoneal infection. Specifically, titers of the Smith strain and rescued virus in the salivary glands, lungs, spleens, livers, and kidneys of the SCID mice at 21 days postinfection were about 5 ؋ 10 5 , 2 ؋ 10 5 , 5 ؋ 10 4 , 5 ؋ 10 3 , and 1 ؋ 10 4 PFU/ml of organ homogenate, respectively; in contrast, titers of RvM37 in these organs were less than 10 2 PFU/ml of organ homogenate. Moreover, the virulence of the mutant virus appeared to be significantly attenuated because none of the SCID mice infected with RvM37 had died by 120 days postinfection, while all animals infected with the wild-type and rescued viruses had died by 26 days postinfection. Our results suggest that M37 probably encodes a virulence factor and is required for MCMV virulence in SCID mice and for optimal viral growth in vivo.

“…This NH 2 -terminal targeting domain constitutes the first UL37x1 antiapoptotic domain, which when combined with a downstream domain (aa 118 to 147) are sufficient to confer its antiapoptotic activity (5,18,19,28,32,34,45). Between the UL37x1 antiapoptotic domains lies an acidic domain (aa 81 to 108), which plays a role in the transactivation of HCMV early gene promoters, whose products are needed for its oriLyt replication (13,31,52). pUL37x1, gpUL37, and pUL37 M dually traffic to the ER and to the mitochondrial outer membrane in transfected and in HCMV-infected cells (2,18,19,(25)(26)(27)42).…”

mentioning

confidence: 99%

Mitochondrial and Secretory Human Cytomegalovirus UL37 Proteins Traffic into Mitochondrion-Associated Membranes of Human Cells

Bozidis

Williamson

Colberg-Poley

2008

Self Cite

The human cytomegalovirus (HCMV) UL37 exon 1 protein (pUL37x1), also known as vMIA, is the predominant UL37 isoform during permissive infection. pUL37x1 is a potent antiapoptotic protein, which prevents cytochrome c release from mitochondria. The UL37x1 NH 2 -terminal bipartite localization signal, which remains uncleaved, targets UL37 proteins to the endoplasmic reticulum (ER) and then to mitochondria. Based upon our findings, we hypothesized that pUL37x1 traffics from the ER to mitochondria through direct contacts between the two organelles, provided by mitochondrion-associated membranes (MAMs). To facilitate its identification, we cloned and tagged the human phosphatidylserine synthase 1 (huPSS-1) cDNA, whose mouse homologue localizes almost exclusively in the MAM. Using subcellular fractionation of stable HeLa cell transfectants expressing mEGFP-huPSS-1, we found that HCMV pUL37x1 is present in purified microsomes, mitochondria, and MAM fractions. We further examined the trafficking of the full-length UL37 glycoprotein cleavage products, which divergently traffic either through the secretory apparatus or into mitochondria. Surprisingly, pUL37 NH2 and gpUL37 COOH were both detected in the ER and MAM fraction, even though only pUL37 NH2 is preferentially imported into mitochondria but gpUL37 COOH is not. To determine the sequences required for MAM importation, we examined pUL37x1 mutants that were partially defective for mitochondrial importation. Deletion mutants of the NH 2 -terminal UL37x1 mitochondrial localization signal were reduced in trafficking into the MAM, indicating partial overlap of MAM and mitochondrial targeting signals. Taken together, these results suggest that HCMV UL37 proteins traffic from the ER into the MAM, where they are sorted into either the secretory pathway or to mitochondrial importation.