XENOPUS INTERSPERSED RNA FAMILIES, OCR AND XR, BIND DNA-BINDING PROTEINS

Interspersed RNA makes up two-thirds of cytoplasmic polyadenylated RNA in Xenopus and sea urchin eggs. Although it has no known function, pr evious work has suggested that at least one family of interspersed RNA , XR, binds Xenopus oocyte proteins, and can influence the rate of tra nslation. We have used two Xenopus repeat families, Ocr and XR, to exp lore their protein binding abilities. Ocr RNA binds the same pattern o f highly abundant oocyte proteins that XR RNA binds, which are believe d to be messenger ribonucleoprotein (mRNP) particle proteins. In addit ion, we show that Ocr RNA binds the Oct-60 protein, a member of the PO U-domain family of transcription factors found in Xenopus oocytes. Usi ng a 32 base pair sequence from the XR repeat in a DNA affinity column two proteins were isolated, 66 kDa and 92 kDa, that together form a c omplex with XR DNA. One of these proteins (92 kDa) also binds XR RNA. We suggest that the role of at least a subset of interspersed RNAs in development may be to bind, and sequester in the cytoplasm, DNA-bindin g proteins until the end of oogenesis.