Kaposi's Sarcoma-associated Herpesvirus K8 is an RNA Binding Protein that Regulates Viral DNA Replication in Coordination With A Noncoding RNA
Kaposi's Sarcoma-associated Herpesvirus K8 is an RNA Binding Protein that Regulates Viral DNA Replication in Coordination With A Noncoding RNA
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DOI：
10.1128/jvi.02177-17
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发表时间：
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影响因子：
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通讯作者：
Yuan Yan
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作者：
Liu Dongcheng;Wang Yan;Yuan Yan
KSHV lytic replication and constant primary infection of fresh cells are crucial for viral tumorigenicity. Virus-encoded b-Zip family protein K8 plays an important role in viral DNA replication in both viral reactivation and de novo infection. The mechanism underlying the functional role of K8 in the viral life cycle is elusive. Here we report that K8 is a RNA binding protein, which also associates with many proteins including other RNA binding proteins. Many K8-involved protein-protein interactions are mediated by RNA. Using a crosslinking and immunoprecipitation (CLIP) procedure combined with high-throughput sequencing, RNAs that are associated with K8 in BCBL-1 cells were identified, that include both viral (PAN, T1.4, T0.7 and etc.) and cellular (MALAT-1, MRP, 7SK and etc.) RNAs. An RNA-binding motif in K8 was defined, and mutation of the motif abolished the ability of K8 binding to many noncoding RNAs as well as viral DNA replication during de novo infection, suggesting that the K8 functions in viral replication are carried out through RNA association. The function of K8 and associated T1.4 RNA was investigated in details and results showed that T1.4 mediates the binding of K8 with ori-Lyt DNA. T1.4-K8 complex physically bound to KSHV ori-Lyt DNA and recruited other proteins and cofactors to assemble replication complex. Depletion of T1.4 abolished the DNA replication in primary infection. These findings provide mechanistic insights into the role of K8 in coordination with T1.4 RNA in regulating KSHV DNA replication during de novo infection.ImportanceGenome wide analyses of the mammalian transcriptome revealed that a large proportion of sequence previously annotated as noncoding region are actually transcribed and give rise to stable RNAs. Emergence of a large number of noncoding RNAs suggests that functional RNA-protein complexes exampled by ribosome or spliceosome are not ancient relics of the last riboorganism but would be well adapted for regulatory role in biology. K8 has been puzzled by its unique characteristic such as multiple regulatory roles in gene expression and DNA replication without DNA binding capability. This study revealed the mechanism underlying its regulatory role by demonstrating that K8 is an RNA binding protein that binds to DNA and initiate DNA replication in coordination with a noncoding RNA. It is suggested that many of K8 functions, if not all, are carried out through its associated RNAs.
