The human cytomegalovirus UL45 gene product is a late, virion-associated protein and influences virus growth at low multiplicities of infection.
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).
Patrone
Marco
M
Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Percivalle
Elena
E
Servizio di Virologia, IRCCS Policlinico San Matteo, Pavia, Italy.
Secchi
Massimiliano
M
Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Fiorina
Loretta
L
Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Pedrali-Noy
Guido
G
Istituto di Genetica Molecolare, CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Zoppé
Monica
M
Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
Baldanti
Fausto
F
Servizio di Virologia, IRCCS Policlinico San Matteo, Pavia, Italy.
Hahn
Gabriele
G
Max von Pettenkofer-Institut, Lehrstuhl für Virologie, LMU-München, München, Germany.
Koszinowski
Ulrich H
UH
Max von Pettenkofer-Institut, Lehrstuhl für Virologie, LMU-München, München, Germany.
Milanesi
Gabriele
G
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.
Gallina
Andrea
A
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.
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
D018797:Cell Cycle Proteins; C446319:UL47 protein, cytomegalovirus; D014764:Viral Proteins; C405947:RRM2B protein, human; D012264:Ribonucleotide Reductases; C486561:Rrm2b protein, mouse