KSHV RTA Plays A Role In Up-regulation Of GBX2 Expression To Promote Angiogenesis And Migration

Kaposi’s sarcoma associated herpesvirus(KSHV),also known as human herpesvirus type 8,is a member of the gamma herpesvirus family,related to Kaposi’s sarcoma(KS),Primary effusion lymphoma(PEL),Multicentric Castleman disease(MCD),and KSHV inflammatory cytokinesyndrome(KICS).KSHV has a two-phase life cycle,which is divided into the latent phase and the lytic phase.In most cases,KSHV is in a latent infection state and will enter the lytic phase under certain exogenous stimuli.RTA is the key switch molecule during KSHV reactivation with potent transcriptional activity which can drive the transition of KSHV from the latent stage to the lytic stage.In addition,KSHV also promotes lytic activation by utilizing a variety of host proteins and signaling pathways.At present,the molecular mechanisms of KSHV reactivation and pathogenesis are still not fully understood.Exploring the viral proteins,host proteins and signaling pathways involved in this process is an important step to understand these mechanisms.It has been shown that KSHV related MCD is often accompanied by overexpression of IL6(Interleukin 6)and viral homologue v IL6 encoded by KSHV.The lytic KSHV antigens can be detected in MCD,indicating that viral lytic replication occurs.Therefore,this study started from the host molecules that regulate the expression of IL6,trying to find the cellular factors which are significantly changed in the process of KSHV reactivation,and exploring their functions.Through literature and data analysis,we found that the m RNA level of Gastrulation brain homeobox 2(GBX2)was significantly upregulated during KSHV lytic reactivation.We also found that the expression levels of v IL6 and v GPCR are increased with the transient over expression of GBX2..Dual-Luciferase reporter gene assay showed that GBX2 might regulate v IL6 and v GPCR through the direct activation of their promoter.RNAi knockdown of GBX2 expression in i SLK.RGB cell showed that inhibition of GBX2 expression could affect the protein abundance of angiogenesis related factor Ang2.Wound healing experiment using i SLK.RGB cell line showed that cell migration was also reduced after knockdown of GBX2 expression.Above results suggested that GBX2 may play an important role in KSHV related pathogenesis.Meanwhile,we also demonstrated that the expression of GBX2 was significantly reduced when the expression of RTA or STAT3 was knockdown,suggesting that RTA and STAT3 are essential for GBX2 overexpression during KSHV reactivation.In summary,this study found that host protein GBX2 can be upregualated during KSHV lytic reactivation,thereby promotes the expression of v IL6,v GPCR and Ang2.This study also demonstrated that GBX2 has effect on cell migration.Meanwhile,the regulatory mechanism of GBX2 during the reactivation of KSHV were preliminarily investigated.This work provides a new insight for understanding of the KSHV life cycle and pathogenesis and basis for the development of novel therapeutics for KSHVrelated diseases.