xl21: A localized maternal transcript in Xenopus laevis

We describe the cloning and characterization of a partial cDNA, x121, that represents an RNA, which is localized in the animal hemisphere of Xenopus oocytes. This RNA is also detected in an animal to vegetal gradient during early cleavage stages. The x121 RNA titer decreases from fertilization through the gastrula stage, after which it is not detectable on northern blots. The amino acid composition of the x121 conceptual protein derived from cDNA sequencing reveals a large number of acidic residues similar in distribution to proteins that function as transcriptional activators.