Figure 5.

Overexpression of a C-terminal fragment of IQGAP1 (IQDN4) inhibits M-MuLV release. (A) Schematic diagram of N-terminal truncations of full-length IQGAP1. Numbers refer to the amino-acid residue of the protein. (B, C) 293T cells were cotransfected with 3 μg of the wild-type proviral DNA (pNCS) and either 6, 9, 12, or 15 μg of the Flag-tagged IQDN4 or IQDN3 expression construct as indicated. Virion proteins from culture media and cell lysates were subjected to Western blot analysis with anti-CA antisera and anti-FLAG antibodies. (D) 239T cells were cotransfected with 3 μg of an HIV-1 proviral DNA (Δ8.9) and increasing levels of IQDN4 as in (B). Virion proteins from culture media and cell lysates were subjected to Western blot analysis with anti-CA antisera and anti-FLAG antibodies. (E) Expression of IQDN4 increases retroviral resistance in Rat2 cells. Equal amounts of protein extracts from the indicated cell lines were subjected to SDS–PAGE, and immunoblotted with anti-FLAG antibodies to evaluate expression of IQDN4. (F) These same lines were then challenged by infection with MuLV vectors expressing the neo^r gene, and the number of G418-resistant colonies was determined after 14 days.