Kaposi's sarcoma-associated herpesvirus ORF45 mediates transcriptional activation of the HIV-1 long terminal repeat via RSK2.
Robust activation of human immunodeficiency virus type 1 (HIV-1) gene expression occurs upon superinfection with Kaposi's sarcoma-associated herpesvirus (KSHV), a common AIDS-associated pathogen. Though the mechanisms underlying this phenotype remain unknown, several KSHV-encoded factors have been reported to stimulate HIV-1 long terminal repeat (LTR) activity. Here, we systematically evaluated the ability of KSHV tegument proteins to modulate the activation of an integrated HIV-1 LTR and revealed that the most potent individual activator is ORF45. ORF45 directs an increase in RNA polymerase II recruitment to the HIV-1 LTR, leading to enhanced transcriptional output. ORF45 is a robust activator of the p90 ribosomal S6 kinases (RSK), and we found that this activity is necessary but not sufficient to increase transcription from the LTR. Of the three widely expressed RSK isoforms, RSK2 appears to be selectively involved in LTR stimulation by both KSHV ORF45 and HIV-1 Tat. However, constitutively active RSK2 is unable to stimulate the LTR, suggesting that ORF45 may preferentially direct this kinase to a specific set of targets. Collectively, our findings reveal a novel transcriptional activation function for KSHV ORF45 and highlight the importance of RSK2 in shaping the transcriptional environment during infection.


OBJECTIVE
Kaposi's sarcoma-associated herpesvirus (KSHV) is a prominent AIDS-associated pathogen. Previous studies have shown that infection of cells containing human immunodeficiency virus type 1 (HIV-1) with KSHV leads to potent stimulation of HIV-1 gene expression by activating the HIV-1 promoter, termed the long terminal repeat (LTR). Here, we compared the abilities of various KSHV proteins to activate gene expression from the HIV-1 LTR and found that KSHV ORF45 is the most potent activator. ORF45 is known to induce cell signaling through ribosomal S6 kinase (RSK) and enhance protein translation. However, we revealed that the activation of a specific isoform of RSK by ORF45 also leads to increased mRNA synthesis from the LTR by the host RNA polymerase. Collectively, our findings provide new insight into the interviral interactions between KSHV and HIV that may ultimately impact disease.
Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
John
J
Karijolich
Department of Cell and Molecular Biology, University of California, Berkeley, California, USA.
Yang
Y
Zhao
Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
Bret
B
Peterson
Department of Cell and Molecular Biology, University of California, Berkeley, California, USA.
Qiang
Q
Zhou
Department of Plant and Microbial Biology, University of California, Berkeley, California, USA Department of Cell and Molecular Biology, University of California, Berkeley, California, USA glaunsinger@berkeley.edu.
Britt
B
Glaunsinger
D000818:Animals; D002460:Cell Line; D060085:Coinfection / Q000201:enzymology* / Q000235:genetics / Q000821:virology; D015658:HIV Infections / Q000201:enzymology* / Q000235:genetics / Q000821:virology; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics* / Q000502:physiology; D006566:Herpesviridae Infections / Q000201:enzymology* / Q000235:genetics / Q000821:virology; D019288:Herpesvirus 8, Human; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D017874:Immediate-Early Proteins; C456286:ORF45 protein, Kaposi's sarcoma-associated herpesvirus; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3