A gammaherpesviral internal repeat contributes to latency amplification.
BACKGROUND
Gammaherpesviruses cause important infections of humans, in particular in immunocompromised patients. The genomes of gammaherpesviruses contain variable numbers of internal repeats whose precise role for in vivo pathogenesis is not well understood.


RESULTS
We used infection of laboratory mice with murine gammaherpesvirus 68 (MHV-68) to explore the biological role of the 40 bp internal repeat of MHV-68. We constructed several mutant viruses partially or completely lacking this repeat. Both in vitro and in vivo, the loss of the repeat did not substantially affect lytic replication of the mutant viruses. However, the extent of splenomegaly, which is associated with the establishment of latency, and the number of ex vivo reactivating and genome positive splenocytes were reduced. Since the 40 bp repeat is part of the hypothetical open reading frame (ORF) M6, it might function as part of M6 or as an independent structure. To differentiate between these two possibilities, we constructed an N-terminal M6STOP mutant, leaving the repeat structure intact but rendering ORF M6 unfunctional. Disruption of ORF M6 did neither affect lytic nor latent infection. In contrast to the situation in lytically infected NIH3T3 cells, the expression of the latency-associated genes K3 and ORF72 was reduced in the latently infected murine B cell line Ag8 in the absence of the 40 bp repeat.


CONCLUSIONS
These data suggest that the 40 bp repeat contributes to latency amplification and might be involved in the regulation of viral gene expression.
Thakur
Nagendra N
NN
Institute of Molecular Immunology, Clinical Cooperation Group Hematopoietic Cell Transplantation, GSF National Research Center for Environment and Health, Munich, Germany.
El-Gogo
Susanne
S
Steer
Beatrix
B
Freimüller
Klaus
K
Waha
Andreas
A
Adler
Heiko
H
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D041681:NIH 3T3 Cells; D016366:Open Reading Frames; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D018144:Rhadinovirus / Q000235:genetics* / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000473:pathology / Q000821:virology; D019562:Viral Load; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D017735:Virus Latency / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics
D014764:Viral Proteins
J Virol. 2000 Aug;74(15):6964-74
10888635
J Virol. 1997 Aug;71(8):5894-904
9223479
Proc Natl Acad Sci U S A. 2000 Jul 18;97(15):8381-5
10890896
Proc Natl Acad Sci U S A. 2000 Jul 18;97(15):8455-60
10890918
J Virol. 2000 Aug;74(16):7451-61
10906198
Philos Trans R Soc Lond B Biol Sci. 2001 Apr 29;356(1408):569-79
11313012
J Virol. 2001 Jun;75(11):4955-63
11333874
J Virol. 2001 Jun;75(12):5692-6
11356978
Immunity. 2001 Oct;15(4):627-36
11672544
Curr Opin Cell Biol. 2002 Jun;14(3):299-304
12067651
Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14759-63
9405686
Nat Med. 1998 Aug;4(8):939-44
9701247
Trends Microbiol. 1998 Jul;6(7):276-82
9717216
Nat Genet. 1998 Oct;20(2):123-8
9771703
Genomics. 1999 Jan 15;55(2):194-201
9933566
J Virol. 1999 Mar;73(3):2321-32
9971815
Nucleic Acids Res. 1999 Mar 15;27(6):1555-7
10037821
Semin Cancer Biol. 1999 Jun;9(3):165-74
10343068
Curr Opin Immunol. 1999 Aug;11(4):371-9
10448140
Curr Opin Microbiol. 1999 Aug;2(4):403-9
10458986
Science. 2005 Feb 4;307(5710):739-41
15692053
J Gen Virol. 2005 Mar;86(Pt 3):561-74
15722515
J Gen Virol. 2005 May;86(Pt 5):1261-7
15831936
Nat Clin Pract Oncol. 2005 Dec;2 Suppl 1:S4-11
16341240
Trends Genet. 2006 Jan;22(1):38-45
16309780
J Virol. 2006 Jun;80(12):6165-70
16731955
J Virol. 2007 Jul;81(13):7300-5
17442722
J Immunol. 2003 Jan 1;170(1):243-51
12496406
J Virol. 2003 Jul;77(13):7308-18
12805429
J Virol. 2003 Oct;77(19):10295-303
12970414
J Cell Sci. 2003 Nov 15;116(Pt 22):4483-91
14576342
Clin Immunol. 2003 Oct;109(1):53-63
14585276
J Gen Virol. 2003 Dec;84(Pt 12):3405-16
14645921
J Virol. 2003 Dec;77(24):13093-105
14645566
Viral Immunol. 2004;17(1):69-77
15018663
Immunity. 2004 Mar;20(3):305-17
15030774
Curr Opin Cell Biol. 2004 Jun;16(3):256-62
15145349
Curr Opin Immunol. 2004 Aug;16(4):456-62
15245739
J Mol Biol. 1967 Jun 14;26(2):365-9
4291934
Acta Virol. 1980 Dec;24(6):468
6111210
Nucleic Acids Res. 1983 Jun 25;11(12):3919-37
6306567
J Virol. 1983 Oct;48(1):135-48
6310141
Nature. 1984 Jul 19-25;310(5974):207-11
6087149
Nat Immunol. 2002 Aug;3(8):733-40
12101398
J Virol. 1985 Dec;56(3):987-95
2999451
J Virol. 1988 Mar;62(3):732-43
2828668
J Virol. 1989 Jul;63(7):3040-50
2542612
J Virol. 1989 Nov;63(11):4609-15
2552144
J Virol. 1990 Jan;64(1):313-21
2152819
Virology. 1989 Dec;173(2):489-98
2556840
Science. 1990 Jun 8;248(4960):1227-30
2112266
Proc Natl Acad Sci U S A. 1992 Mar 1;89(5):1827-31
1542678
Science. 1994 Dec 16;266(5192):1865-9
7997879
Nature. 1995 Jun 22;375(6533):685-8
7540727
Proc Natl Acad Sci U S A. 1996 Dec 10;93(25):14862-7
8962146
J Gen Virol. 1995 Apr;76 ( Pt 4):779-90
9049323
J Virol. 2000 Aug;74(15):7016-23
10888640