Fig. 1. Sqd and Hrb27C interact. (A) A schematic of the SqdA protein [321 amino acids (aa)] containing two RNA-binding domains (RRMs) (striped boxes), an M9-like nuclear transport motif (black box) and a glycine rich C-terminal region (hatched box). The underlined region represents the region used as bait in the yeast two-hybrid screen. The Hrb27C protein (422 aa) also contains two RNA-binding motifs (striped boxes). We isolated four different clones of Hrb27C: two contain all but the first 11 amino acids, one contains all but the first 28 amino acids and one is truncated to exclude the first 109 amino acids (underlined). (B) The Hrb27C-activation domain (AD) fusion interacts with the LexA-SqdA fusion but not with LexA alone or a LexA-p53 fusion. The AD alone does not interact with any LexA fusion proteins. (C) Western blot probed for Hrb27C and Sqd after immunoprecipitation (IP) from ovarian lysate with either Sqd or SpnF antibody in the absence (–) or presence (+) of RNAse A. Hrb27C co-purifies in an RNA-dependent manner with Sqd but not SpnF. WCL, whole cell lysate (one-tenth volume).