Induction of RNA-binding proteins in mammalian cells by DNA-damaging agents

A technique to detect RNA-binding proteins (RBP) involving hybridization of RNA probe to proteins transferred to a membrane was used to study RBP in different mammalian cells and in cells after genotoxic stress. With this approach, up to 13 proteins of different sizes were detected in crude nuclear extracts by using a viral RNA probe consisting of the trans-activation-responsive (TAR) element of human immunodeficiency virus type 1 (HIV-1). The TAR RNA probe contains a stem-loop structure found in nascent HIV-1 transcripts. A G+C-rich probe with similar structure also bound to many of these RBP. Only a 102-kDa protein strongly bound to other RNA probes lacking this structure, while a probe with an A+U-rich stem-loop structure fail to bind most RBP, thus indicating a RNA secondary structure preference. The expression of these RBP varied substantially in nine different human and hamster cell lines, with no detectable RBP in two human myeloid lines. Evidence for induction of these RBP was found in six of seven lines after treatment with DNA-damaging agents; UV radiation was the most effective agent. In Chinese hamster ovary cells, which showed the strongest response, all five RBP present in untreated cells rapidly increased in activity after UV irradiation, and eight additional RBP were detected. The induction of these RBP by DNA-damaging agents indicates one or more possible roles for these proteins in the cellular response to genotoxic stress and in viral activation after such stress.