YY1 (Yin Yang 1) is present in the Xenopus oocyte cytoplasm as a constituent of messenger ribonucleoprotein complexes (mRNPs). Association of YY1 with mRNPs requires direct RNA-binding activity. Previously, we have shown YY1 has a high affinity for U-rich RNA; however, potential interactions with plausible in vivo targets have not been investigated. Here we report a biochemical characterization of the YY1–RNA interaction including an investigation of the stability, potential 5′-methylguanosine affinity, and specificity for target RNAs. The formation of YY1–RNA complexes in vitro was highly resistant to thermal, ionic, and detergent disruption. The endogenous oocyte YY1–mRNA interactions were also found to be highly stable. Specific YY1–RNA interactions were observed with selected mRNA and 5S RNA probes. The affinity of YY1 for these substrates was within an order of magnitude of that for its cognate DNA element. Experiments aimed at determining the potential role of the 7-methylguanosine cap on RNA-binding reveal no significant difference in the affinity of YY1 for capped or uncapped mRNA. Taken together, the results show that the YY1–RNA interaction is highly stable, and that YY1 possesses the ability to interact with structurally divergent RNA substrates. These data are the first to specifically document the interaction between YY1 and potential in vivo targets.
Morphological and Biochemical Characterization of Macrophages Activated by Carrageenan and Lipopolysaccharide In Vivo