Activation of latent Kaposi's sarcoma-associated herpesvirus by demethylation of the promoter of the lytic transactivator

doi:10.1073/pnas.051004198

Activation of latent Kaposi's sarcoma-associated herpesvirus by demethylation of the promoter of the lytic transactivator

^*Department of Microbiology, Osaka University Medical School, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan; ^†Department of Microbiology, Hyogo Medical College, Nishinomiya, Hyogo 663-8501, Japan; and ^§Institute of Infectious Diseases, University of Milano, and ^‡Department of Pathology, Luigi Sacco Hospital, Milan 20157, Italy

Communicated by Bernard Roizman, University of Chicago, Chicago, IL (received for review November 11, 2000)

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) is strongly linked to Kaposi's sarcoma, primary effusion lymphomas, and a subset of multicentric Castleman's disease. The mechanism by which this virus establishes latency and reactivation is unknown. KSHV Lyta (lytic transactivator, also named KSHV/Rta), mainly encoded by the ORF 50 gene, is a lytic switch gene for viral reactivation from latency, inasmuch as it is both essential and sufficient to drive the entire viral lytic cycle. Here we show that the Lyta promoter region was heavily methylated in latently infected cells. Treatment of primary effusion lymphoma-delivered cell lines with tetradecanoylphorbol acetate caused demethylation of the Lyta promoter and induced KSHV lytic phase in vitro. Methylation cassette assay shows demethylation of the Lyta promoter region was essential for the expression of Lyta. In vivo, biopsy samples obtained from patients with KSHV-related diseases show the most demethylation in the Lyta promoter region, whereas samples from a latently infected KSHV carrier remained in a methylated status. These results suggest a relationship among a demethylation status in the Lyta promoter, the reactivation of KSHV, and the development of KSHV-associated diseases.

Footnotes

↵ ¶ To whom reprint requests should be addressed. E-mail: yamanisi{at}micro.med.osaka-u.ac.jp.
Abbreviations:

KSHV,

Kaposi's sarcoma-associated herpesvirus;

HHV,

human herpesvirus;

Lyta,

KSHV lytic transactivator, also named KSHV Rta;

KS,

Kaposi's sarcoma;

PEL,

primary effusion lymphomas;

MCD,

multicentric Castleman's disease;

TPA,

phorbol 12-tetradecanoate 13-acetate;

IE,

immediate-early;

IFA,

immunofluorescence antibody assay;

CpG,

5′ cytosine-guanine