Gene product of Moloney murine leukemia virus required for proviral integration is a DNA-binding protein.

The 3'-terminal portion of the retroviral pol gene encodes a function required for the formation of the integrated provirus soon after infection of sensitive cells. To permit the isolation of large quantities of the gene product, we expressed various portions of the pol gene of Moloney murine leukemia virus (M-MuLV) as trpE fusion proteins in Escherichia coli. The proteins were found to exhibit strong DNA-binding activity after extraction and renaturation by two different procedures. In the first method, proteins separated by polyacrylamide gel electrophoresis were blotted to nitrocellulose and assayed when bound to the support. The second procedure involved the isolation of proteins in an insoluble fraction, solubilization with guanidine, and renaturation. The characteristics of the binding activity are described and compared with those of authentic viral protein.