RNA-binding protein PTBP1 mediates HSV-1 attachment and infection through regulation of heparan sulfate 3-O-sulfotransferase gene expression.

BACKGROUND: The RNA-binding protein polypyrimidine tract-binding protein 1 (PTBP1), also known as heterogeneous nuclear ribonucleoprotein I (hnRNP I), mediates gene expression through splicing regulation. Its role in virus infection is undefined. RESULTS: We show that genetic ablation of PTBP1 renders cell resistant to herpes simplex virus 1 (HSV-1) infection. HSV-1 utilizes 3-O-sulfated heparan sulfate proteoglycans (HSPGs) for attachment and for infection of epithelial cells. We found that knockout of PTBP1 expression resulted in loss of HS3ST3A1 and HS3ST3B1, heparan sulfate glucosaminyl 3-O-sulfotransferase genes for 3-O-sulfation of the heparan sulfate (HS) chains of HSPGs. Each of the HS3ST3A1/HS3ST3B1 genes is composed of 2 exons separated by an extraordinarily long intron whose removal requires PTBP1-associated looping. We found that PTBP1 interacted with the intronic region of HS3ST3A1/HS3ST3B1 pre-mRNAs and modulated their processing to mRNA. The essential role of PTBP1 in functional HS3ST3A1 expression and in HSV-1 infection was demonstrated by ectopic re-expression in the knockout (ko) cells. In addition, we showed that targeting PTBP1 expression by microRNA mimics reduced disease symptoms in a mouse herpetic stromal keratitis (HSK) model. CONCLUSIONS: The results demonstrate that PTBP1 mediates HSV-1 infection of epithelial cells through splicing regulation of HS3ST3A1/HS3ST3B1. These studies provide a new area for novel therapeutic strategies through splicing regulation.