title: The human cytomegalovirus UL45 gene product is a late, virion-associated protein and influences virus growth at low multiplicities of infection.
abstract: Human cytomegalovirus (HCMV) encodes a protein related to the large (R1) subunit of ribonucleotide reductase (RR), but does not encode the corresponding small (R2) subunit. The R1 homologue, UL45, lacks many catalytic residues, and its impact on deoxyribonucleotide (dNTP) production remains unknown. Here, UL45 is shown to accumulate at late stages of infection and to be a virion tegument protein. To study UL45 function in its genome context, UL45 was disrupted by transposon insertion. The UL45-knockout (UL45-KO) mutant exhibited a growth defect in fibroblasts at a low m.o.i. and also a cell-to-cell spread defect. This did not result from a reduced dNTP supply because dNTP pools were unchanged in resting cells infected with the mutant virus. Irrespective of UL45 expression, all cellular RR subunits - S-phase RR subunits, and the p53-dependent p53R2 - were induced by infection. p53R2 was targeted to the infected cell nucleus, suggesting that HCMV diverts a mechanism normally activated by DNA damage response. Cells infected with the UL45-KO mutant were moderately sensitized to Fas-induced apoptosis relative to those infected with the parental virus. Together with the report on the UL45-KO endotheliotropic HCMV mutant (Hahn et al., J Virol 76, 9551-9555, 2002), these data suggest that UL45 does not share the prominent antiapototic role attributed to the mouse cytomegalovirus homologue M45 (Brune et al., Science 291, 303-305, 2001).
authors.affiliation: Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Patrone
authors.affiliation: Servizio di Virologia, IRCCS Policlinico San Matteo, Pavia, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Percivalle
authors.affiliation: Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Secchi
authors.affiliation: Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Loretta
authors.initials: L
authors.lastname: Fiorina
authors.affiliation: Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Pedrali-Noy
authors.affiliation: Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Zoppé
authors.affiliation: Servizio di Virologia, IRCCS Policlinico San Matteo, Pavia, Italy.
authors.forename: Fausto
authors.initials: F
authors.lastname: Baldanti
authors.affiliation: Max von Pettenkofer-Institut, Lehrstuhl für Virologie, LMU-München, München, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Hahn
authors.affiliation: Max von Pettenkofer-Institut, Lehrstuhl für Virologie, LMU-München, München, Germany.
authors.forename: Ulrich H
authors.initials: UH
authors.lastname: Koszinowski
authors.affiliation: Department of Medicine and Surgery, San Paolo Hospital, University of Milano, via A. di Rudinı ` 8, I-20142 Milano, Italy.|Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Milanesi
authors.affiliation: Department of Medicine and Surgery, San Paolo Hospital, University of Milano, via A. di Rudinı ` 8, I-20142 Milano, Italy.|Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gallina
mesh_terms: D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000201:enzymology / Q000502:physiology*; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D012264:Ribonucleotide Reductases / Q000096:biosynthesis; D016196:S Phase; D013997:Time Factors; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014771:Virion / Q000201:enzymology*; D014779:Virus Replication
chemical_list: D018797:Cell Cycle Proteins; C446319:UL47 protein, cytomegalovirus; D014764:Viral Proteins; C405947:RRM2B protein, human; D012264:Ribonucleotide Reductases; C486561:Rrm2b protein, mouse