Inhibition of retroviral RNA production by ZAP, a CCCH-type zinc finger protein

Cells have evolved multiple mechanisms to inhibit viral replication. To identify previously unknown antiviral activities, we screened mammalian complementary DNA (cDNA) libraries for genes that prevent infection by a genetically marked retrovirus. Virus-resistant cells were selected from pools of transduced clones, and an active antiviral cDNA was recovered. The gene encodes a CCCH-type zinc finger protein designated ZAP. Expression of the gene caused a profound and specific loss of viral messenger RNAs (mRNAs) from the cytoplasm without affecting the levels of nuclear mRNAs. The finding suggests the existence of a previously unknown machinery for the inhibition of virus replication, targeting a step in viral gene expression.