Abstract
The coupling of mRNA processing steps is essential for precise and efficient gene expression. The human transcription/export (hTREX) complex is a highly conserved multi-protein complex responsible for eukaryotic mRNA stability and nuclear export. We have previously shown that the Kaposi’s sarcoma-associated open reading frame 57 (ORF57) protein orchestrates the recruitment of the hTREX complex onto viral intronless mRNA, forming a stable and export-competent viral ribonucleoprotein particle (vRNP). Recently, additional cellular proteins, namely CHTOP, CIP29 and POLDIP3 have been proposed as novel hTREX components. Herein, we extend our previous research and provide evidence that ORF57 interacts with CHTOP and CIP29, in contrast to POLDIP3. Moreover, depletion studies show both CHTOP and CIP29 effect ORF57-mediated viral mRNA processing. As such, these results suggest both CHTOP and CIP29 are hTREX components and are recruited to an ORF57-mediated vRNP.
Highlights
The coupling of mRNA processing steps is essential for precise and efficient gene expression
We have previously shown that the Kaposi’s sarcoma-associated open reading frame 57 (ORF57) protein orchestrates the recruitment of the human transcription/export (hTREX) complex onto viral intronless mRNA, forming a stable and exportcompetent viral ribonucleoprotein particle
The hTREX complex serves as a binding platform for Nxf1 on herpesvirus mRNAs, forming a stable and export-competent viral ribonucleoprotein particle
Summary
Interactions between KSHV ORF57 and the novel human TREX proteins, CHTOP and CIP29. The coupling of mRNA processing steps is essential for precise and efficient gene expression. We have previously shown that ORF57 recruits hTREX components Aly, UAP56 and the THO sub-complex onto viral intronless mRNA to facilitate vRNP formation (Boyne et al, 2008; Jackson et al, 2014). We extend our previous research and provide evidence that ORF57 interacts with these putative hTREX components This provides novel evidence that these cellular proteins may be part of hTREX and confirms that ORF57 recruits the complete hTREX complex onto viral mRNA in order to facilitate mRNA stability and export. For mRNA export assays, cells were transfected with CIP29-, CHTOP- or POLDIP3-specific siRNA or scramble control for 72 h, to allow sufficient protein depletion.
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