Fig. 4. K(10) but not grk mRNA is in an immunoprecipitable complex with Orb protein. Anti-Orb or anti-Dorsal antibody was used for immunoprecipitation of wild-type ovary extracts. RNA isolated from the immunoprecipitates (IP) and from the total extracts was reverse transcribed with an anchored oligo(dT) primer (see Materials and Methods) and the resulting cDNAs were subjected to PCR amplification using the anchored primer and gene-specific primers for either K(10), grk or nos. The amplification products were displayed by electrophoresis and blotting to nitrocellulose and the filters were then hybridized with gene specific probes. K(10) sequences can be RT-PCR amplified from the Orb IP sample, as well as from the total RNA pool, but not from the Dorsal IP sample (middle panel). In both the Orb IP and the total samples, the K(10) probe hybridizes to a prominent band and an upward smear. The prominent band corresponds in size to a PCR amplification product extending from the K(10) primer in the 3' UTR to the beginning of the poly(A) tail. The smear arises from hybridization of the anchored oligo dT primer at different sites in the poly(A) tail. Neither nos PCR products (left panel) nor grk PCR products (right panel) could be detected in the Orb IP lanes, but could be amplified from the total RNA pool. As expected, no amplification products were observed when the RT step was omitted.